4.0 STORMWATER - Hamilton City Council · development, to Council’s standards, shall be at the...

Section 4 Stormwater

4.0 STORMWATER CONTENTS

4.0 STORMWATER ........................................................................................................................................ I 4.1 Introduction ................................................................................................................................. 4-1

4.1.1 Objectives ...................................................................................................................... 4-1 4.1.2 Alteration to Existing Structure ...................................................................................... 4-2 4.1.3 Waikato Regional Council Resource Consents Requirements ..................................... 4-2 4.1.4 Hamilton City Council Comprehensive Consent for Stormwater Discharge to Land and

Water ............................................................................................................................. 4-2 4.1.5 Integrated Catchment Management Planning .............................................................. 4-3 4.1.6 Stormwater Management Prioritisation ......................................................................... 4-3 4.1.7 Effects of Land Use on Receiving Waters..................................................................... 4-3 4.1.8 System Components ..................................................................................................... 4-3 4.1.9 Catchments and Off-Site Effects ................................................................................... 4-4 4.1.10 Discharges .................................................................................................................... 4-4

4.2 Design ........................................................................................................................................ 4-6 4.2.1 Design Life .................................................................................................................... 4-6 4.2.2 Approved Materials ....................................................................................................... 4-6 4.2.3 System Design .............................................................................................................. 4-6 4.2.4 Design Criteria ............................................................................................................. 4-10 4.2.5 Watercourses .............................................................................................................. 4-21 4.2.6 Piped System Layout .................................................................................................. 4-23 4.2.7 Manholes ..................................................................................................................... 4-23 4.2.8 Connections ................................................................................................................ 4-23 4.2.9 Catchpits...................................................................................................................... 4-27 4.2.10 Outlets and Inlets ........................................................................................................ 4-28 4.2.11 Culverts ....................................................................................................................... 4-29 4.2.12 Weirs ........................................................................................................................... 4-31 4.2.13 Subsoil Drains ............................................................................................................. 4-31 4.2.14 Soakage Devices ........................................................................................................ 4-32 4.2.15 Stormwater Treatment and Detention Devices Design ............................................... 4-34

4.3 Construction and Maintenance ................................................................................................ 4-43 4.3.1 Pipeline Construction .................................................................................................. 4-43 4.3.2 Catchpits...................................................................................................................... 4-43 4.3.3 Connections ................................................................................................................ 4-43 4.3.4 Outlets ......................................................................................................................... 4-44 4.3.5 Stormwater Treatment and Detention Devices ........................................................... 4-44

4.4 Defects Liability ....................................................................................................................... 4-49 4.4.1 Defects Liability Periods .............................................................................................. 4-49 4.4.2 Defects Maintenance Requirements ........................................................................... 4-50 4.4.3 Final Defects Inspection Criteria ................................................................................. 4-52

4.5 Approval of Proposed Works ................................................................................................... 4-54 4.5.1 Piped network .............................................................................................................. 4-54 4.5.2 Stormwater Treatment and Detention Devices ........................................................... 4-55

LIST OF APPENDICES Appendix A Forms and Checklists ............................................................................................................... 4-57 Appendix B Drawings .................................................................................................................................. 4-58


LIST OF FIGURES Figure 4-1: Hamilton City Flood Hazard Classification Matrix ...................................................................... 4-10 Figure 4-2: Overland Flow Graph ................................................................................................................. 4-14 Figure 4-3: Connections for Single Development or Subdivision ................................................................. 4-25 Figure 4-4: Connections to a right of way ..................................................................................................... 4-26 Figure 4-5: Connections for Multi Unit Developments .................................................................................. 4-27 Figure 4-6: Stormwater Wetland Staged Landscape Planting ..................................................................... 4-41 LIST OF TABLES Table 4-1: Minimum Design Summary ........................................................................................................... 4-7 Table 4-2: Design Level of Service ............................................................................................................... 4-11 Table 4-3: Runoff Coefficients ...................................................................................................................... 4-11 Table 4-4: Runoff Coefficients Refined ......................................................................................................... 4-12 Table 4-5: Current Rainfall............................................................................................................................ 4-15 Table 4-6: Adjusted Rainfall Data – 2.08 degrees Celsius ........................................................................... 4-16 Table 4-7: Adjusted Rainfall Data – 3.0 degrees Celsius ............................................................................. 4-16 Table 4-8: Present Climate – For Assessing Pre-Development Flows ........................................................ 4-17 Table 4-9: Incorporating 2.08 degrees Celsius Climate Change – For Assessing Post – Development Flows 4-17 Table 4-10: Incorporating 3.0 degrees Celsius climate change – Consider the Flooding Consequences of This Scenario ................................................................................................................................................ 4-18 Table 4-11: Infill Development Stormwater Level of Service, Return Period and Runoff Coefficient .......... 4-18 Table 4-12: Volumetric Runoff Coefficients .................................................................................................. 4-18 Table 4-13: Loss Coefficients for Bends....................................................................................................... 4-19 Table 4-14: Minimum Pipe Sizes .................................................................................................................. 4-20 Table 4-15: Flooding Freeboard requirements ............................................................................................. 4-20 Table 4-16: Road Flooding Freeboard Requirements .................................................................................. 4-21 Table 4-17: Rainfall Intensity Return Period (ARI) for Infill Residential Development ................................. 4-24 Table 4-18: Culvert Design Storms .............................................................................................................. 4-30 Table 4-19: Soakage Thresholds ................................................................................................................. 4-32 Table 4-20: Groundwater Seasonal Adjustments ......................................................................................... 4-34 Table 4-21: Planting Zones .......................................................................................................................... 4-39 Table 4-22: Approved Plant Species ............................................................................................................ 4-42 Table 4-23: Swale Planting - Velocity/Grade Matrix ..................................................................................... 4-43 Table 4-25: Approved Mulching .................................................................................................................... 4-48 Table 4-26: Defects and Liability Periods ..................................................................................................... 4-49 Table 4-27: Defects Period Maintenance Schedule ..................................................................................... 4-50 Table 4-28: Planting Establishment .............................................................................................................. 4-52 Table 4-29: Minimum Inspection Requirements ........................................................................................... 4-53 Table 4-30: Stormwater Devices Transfer Process ...................................................................................... 4-55 Table 4-31: Forms and Checklists ................................................................................................................ 4-57


Page 4-1 Last Updated: 3 December 2012

4.1 Introduction

This section sets out requirements for the design and construction of stormwater systems for land development and subdivision. The significant issues for stormwater management are the protection of people, property, infrastructure, and the receiving environment. Stormwater management requires the integration of land use, infrastructure and ecological factors. A catchment-based approach is required with consideration of changes in catchment hydrology, rainfall patterns from climate change effects, and increased intensification in developed areas of the City.

Opportunities exist with stormwater design to use or replicate the natural drainage system. For example grassed swales, natural or artificial waterways, ponds and wetlands, may in certain circumstances be not only part of the stormwater system, but also a preferred solution especially if low impact on receiving waters downstream is critical.

Low impact design is Council’s preferred approach, particularly where there is a requirement to replicate the pre-development hydrological regime. Nevertheless, piped stormwater systems will often be required either in support of low impact systems or as the primary system. Stormwater systems serve a number of purposes including; the management of storm surface water runoff, treatment of such runoff, and groundwater control. All aspects need to be considered in design and achieved with minimal adverse effects on the environment.

Council has developed the concept of ‘water-sensitive’ techniques to incorporate ‘green’, low impact, sustainable thinking with the requirements of the Waikato Tainui Raupatu Claims (Waikato River) Settlement Act 2010, considering for example, the inclusion of traditional food and fibre plants within riparian areas.

The definition of water-sensitive techniques for Council is included in the General Section of this ITS.

4.1.1 Objectives The main objective of a stormwater system is to manage stormwater runoff to minimise flood damage and adverse effects on the environment.

The stormwater system shall include:

a) Provision of drainage either within the boundary or at the boundary for all developments

b) Facilitation of ground water recharge

c) A design and construct infrastructure that minimises lifecycle costs

d) A design life of 100 years

e) Meeting Council's levels of service in relation to stormwater management

f) Minimised adverse environmental and community impact, open watercourses are expected to be retained

g) Protection from adverse effects to aquatic ecosystems

h) Compliance with environmental requirements

i) Adequate system capacity to service the fully developed catchment (upstream and downstream properties)


-2 Last Updated: 3 December 2012

j) Application of water-sensitive techniques

k) Integrated Three Waters Catchment Management

l) Avoid cross connections with the wastewater system

m) Avoid pumped solutions

n) Use biotechnical slope stability treatments where feasible

In addition, all stormwater design must:

a) Be consistent with national, regional and local statutory planning documents

b) Not increase peak discharge rates to, or flow volumes in, stormwater receiving waters unless it is demonstrated that there are no additional adverse effects on the environment or downstream properties as a result of such increase

c) Comply with any future stormwater bylaw

d) Comply with Council’s Comprehensive Consent for the discharge of stormwater to land and water

Council encourages early liaison and consultation between the Developer and Council and affected parties prior to commencement of design; this will benefit all parties as it will ensure that sufficient prerequisite information is available to undertake the design.

4.1.2 Alteration to Existing Structure

Any alteration of the existing wastewater network to achieve compliance of the new development, to Council’s standards, shall be at the Developer’s cost.

4.1.3 Waikato Regional Council Resource Consents Requirements

Resource consents from Waikato Regional Council will be required for all works within a stream or river and any direct ‘discharge’ to a waterway unless it can be shown to be a permitted activity in the Regional Plan.

4.1.4 Hamilton City Council Comprehensive Consent for Stormwater Discharge to Land and Water

Individual resource consents from Waikato Regional Council are required for all new stormwater discharges. Once all Hamilton City Council requirements have been met this consent can be surrendered and the discharge will be managed under Council’s Comprehensive Resource Consent.

In order for this to occur the stormwater network shall be designed and constructed as per an approved Stormwater Management Plan, requirements of which are incorporated into Council’s Integrated Catchment Management Plan.

Council encourages early consultation between the Developer and Council staff to achieve:

• Mutual design outcomes, particularly understanding the site specific and ICMP requirements

• Consistency of discharge activity with requirements of the Councils Comprehensive Consent



4.1.5 Integrated Catchment Management Planning All design shall be in accordance with an approved ICMP or WIA.

4.1.6 Stormwater Management Prioritisation In selecting an acceptable engineering solution to stormwater management the following hierarchy shall be adopted.

a) Retention for reuse

b) Soakage techniques

c) Detention and gradual release to a watercourse

d) Detention and gradual release to stormwater reticulation

All effort should be made to either reuse or provide ground soakage before stormwater design incorporates discharge to a watercourse or stormwater reticulation.

4.1.7 Effects of Land Use on Receiving Waters Impervious surfaces and piped stormwater systems associated with development have an effect on catchment hydrology. Faster runoff of storm flows, reduction in base flows, and accelerated channel erosion and depositions alter the hydrology and adversely affect the quality of receiving waters. Exceedances have implications for the biodiversity of the aquatic biological community and post development maintenance requirements on systems such as stormwater treatment devices, streams and channels.

To mitigate these impacts, developments are to achieve a neutral hydrological regime where any increases are minimised.

Hydrological neutrality can be partly achieved when the maximum rate of discharge and peak flood levels post-development are no greater than pre-development and infiltration and base flow characteristics are not significantly altered.

However peak flow neutrality achieved using substantial detention storage results in a significantly extended duration of peak flow. Therefore in the absence of more detailed assessment of stream stability, the discharges from detention structures leading to Council pipes or stream networks shall be constrained to 80% of the pre-development peak flow rate. The effects of rural-residential and pre-urban development runoff rates on receiving waters are generally less significant. The modification to stream hydrology is generally minor. However, any reduction in riparian vegetation increases sediment loads and nutrient concentrations are likely to reduce aquatic biodiversity.

4.1.8 System Components The stormwater system conveys storm surface runoff and shallow groundwater from the point of interception to soakage areas, detention and treatment areas, or the point of discharge to receiving waters. Components of the primary system may include (but not limited to) wetlands, dry detention basins, rain gardens, swales and filters, pipelines,inlet/outlet structures and soakage areas.

Secondary systems incorporate the use of overland flow paths to convey primary system overflows.



4.1.9 Catchments and Off-Site Effects All stormwater systems shall provide for the management of stormwater runoff from within the land being developed together with any runoff from upstream catchments.

Upstream flood levels shall not be increased by any downstream development unless the designer demonstrates that any increase will have minimal minor impact on the upstream properties.

The outcome of any development shall be that the design of the stormwater network avoids adverse scour, erosion and sediment deposition on land, property and the beds of stormwater receiving water bodies; adverse flooding of land, property and stormwater receiving water bodies; and adverse effects on aquatic ecosystems.

4.1.10 Discharges 4.1.10.1 Discharge into a Stream or Watercourse

The uncontrolled discharge of stormwater into streams is not acceptable. In areas where reuse and soakage are not sufficient, but a stream or watercourse is accessible from the site, the stormwater may be drained to the water course provided that the following conditions are met.

a) The design and construction is as per an approved ICMP or CMP. In the absence of an approved ICMP the Developer should contact Council to discuss what treatment is necessary prior to discharge.

b) A suitable outfall and dissipating structure shall be constructed at the outlet to ensure no localised erosion of the watercourse occurs. This structure shall be specifically designed in such a way as to blend in with the immediate natural surroundings.

c) The direction of the discharge shall be aligned with the natural downstream flow as much as practicable so as to prevent erosion of the opposite stream bank. In situations where erosion of the opposite bank is unavoidable, appropriate mitigation measures will be required.

d) No obstructions are to be placed in a watercourse that will impede the natural flow unless these are installed as part of an approved stormwater management system.

e) Individual properties which border onto a stream should discharge their stormwater in a dispersed manner, via a well vegetated flow dispersal device, into the stream to avoid causing erosion.

f) Where the downstream primary stormwater drainage system consists of lined channels only (i.e. no natural streams or watercourses) and the stormwater constraints relate solely to a lack of capacity in the primary drainage system, the discharge from the site for the 10% and 50% AEP runoff events shall be attenuated to the pre-development flows.

g) Suitable detention and treatment devices are proposed, constructed and maintained in accordance with an approved ICMP or WIA. The devices shall be operated and maintained by the Developer to provide best practicable stormwater treatment efficiency at all times until the asset is vested.

Overland flow paths shall be provided in accordance with Section 4.2.3.3 to cater for events exceeding the capacity of the primary system and occasions when the primary drainage system fails.



4.1.10.2 Discharge into the Public Stormwater Network

Council has no legal obligation to provide any property within the City with a connection to a public stormwater network. The Council currently provides a public stormwater network to most areas of the city, however in some areas the system is already at capacity.

As a guideline, after reuse, soakage and natural drainage lines have been exhausted, small developments can detain and connect to the public stormwater network where this is within 30m from the property boundary. Where the network is further away, then a kerb outlet solution is allowable (refer Section 4.1.10.4). Developments requiring discharges greater than 300mm diameter will require specific assessment.

Stormwater treatment and detention will be required prior to discharge to the Council’s network.

Overland flow paths shall be provided in accordance with Section 4.2.3.3 to cater for events exceeding the capacity of the primary system and occasions when the primary drainage system fails.

4.1.10.3 Discharge to a Council Owned Reserve

In situations where a property borders onto a Council owned reserve and the natural flow of stormwater is in the direction of the reserve, it may be appropriate to discharge stormwater to the reserve provided that this does not adversely affect the amenity value or function of the reserve in any way or create any geotechnical or flooding liability issues for Council. Stormwater discharge to a Council owned reserve may be allowed subject to the following.

a) The design and construction is as per an approved ICMP or CMP. In the absence of an approved ICMP the Developer should contact Council to discuss what treatment is necessary prior to discharge to land.

b) Prior approval shall be obtained in writing from Council and any other relevant landholders that may be affected.

c) Stormwater from all impervious areas on the lot shall be mitigated on site to ensure that total runoff volumes and peak flow rates up to the 2% AEP event are mitigated to as close to the pre-development levels as possible.

d) The stormwater shall be discharged in a dispersed manner within the lot via a well vegetated flow dispersal device. If suitable vegetation does not already exist, this shall be planted according to a planting plan to be approved by Council.

e) The receiving reserve area shall be well vegetated or grassed, not susceptible to erosion and have no geotechnical constraints. Where requested by the Council, a report by a suitably qualified professional geotechnical engineer shall be provided to support any application to discharge stormwater to a reserve area.

f) Alternatively, the mitigated stormwater discharge may be piped to an appropriate outfall point within the reserve approved by the Council for that purpose. Council may, at its discretion, require that any such pipe be installed by thrusting techniques to minimise damage and disruption to the reserve.

g) The stormwater discharge shall not compromise any existing or planned structures or parks assets and shall not impede access or reduce the amenity value of the reserve.

h) Overland flow from the reserve shall not create, or exacerbate existing, flooding or erosion problems.



i) Suitable detention and treatment devices are proposed, constructed and maintained in accordance with an approved ICMP or WIA. The devices shall be operated and maintained by the Developer to provide best practicable stormwater treatment efficiency at all times until the asset is vested.

j) All WRC requirements and the Council’s Comprehensive Consent for the discharge of stormwater to land and water shall be met.

4.1.10.4 Discharge to the Road Kerb

Stormwater discharge to a road kerb as a primary means of disposal is not an acceptable solution for stormwater disposal from new developments in ‘Greenfields’ areas. However the use of kerbed roads as overland flow paths is desirable.

In some areas there is a public stormwater drainage system which serves the road network and some properties currently discharge their stormwater onto the roads and ultimately into the road drainage network. This system was generally not designed for the additional stormwater flows and there is no right to utilise the road for primary drainage purposes. As a principle, all sites must minimise discharges of stormwater onto the city's roads.

4.2 Design

4.2.1 Design Life All stormwater systems shall be designed and constructed for an asset life of at least 100 years. Some components of detention and treatment devices such as wetlands, rain gardens and other systems will require earlier renovation or replacement. These assets will require an approved operations and maintenance manual which details the replacement needs of the assets.

Where any proposed device is designed with an asset life less than 100 years, this decision shall be justified in design documentation and the asset renewal requirements fully documented in a Operations and Maintenance Plan which shall be provided to Council for approval.

4.2.2 Approved Materials Refer to the Approved Materials Section 9.

4.2.3 System Design Stormwater systems shall be considered as the total system protecting people, land, infrastructure, and the receiving environment. A stormwater system consists of:

a) A primary system designed to accommodate a specified design rainfall event appropriate for the zone; and

b) A secondary system to ensure that the effects of stormwater runoff from events that exceed the capacity of the primary system are managed, including occasions when there are blockages in the primary system.

The design shall be in accordance with

Table 4-1 below unless the approved ICMP/CMP or relevant District Plan requires different values.



Table 4-1: Minimum Design Summary

Criteria Greenfield development Infill or re-development

Design calculations Computerised modelling – liaise with Council

Rational method up to 10ha, then computerised model

Runoff coefficients Based on Zoning – Table 4-3 Based on Zoning – Table 4-3

Time of concentration

Calculated, with minimum of 10 minutes

Calculated, with minimum of 5 minutes

Erosion control Disposal Hierarchy Section 4.1.6 and Extended detention1 24 mm, discharge limited to 90% of pre-development 2 and 10 year storm runoff always and also 80% of pre-development 100 year ARI runoff when there is downstream flooding2.

Manage via hierarchy Section 4.1.6 and discharge excess primary flow to reticulation or open water bodies at 80% of the pre-development rates.

Flow volume mitigation

Match pre-development volumes to 10 Year ARI event

Match pre-development to level of service for each zone – refer

Table 4-2

Primary3 system LOS4

As per zone -

Table 4-2

As per zone -

Table 4-2

Secondary flow design

100 year ARI event plus freeboard Minimum of 50 year ARI event, document impact of 100 year ARI event plus freeboard

Water quality design Disposal Hierarchy5 and Treatment Train approach

Disposal Hierarchy

Water quality storm 1/3 of 24-hour 2-year ARI storm 1/3 of 24-hour 2-year ARI storm

4.2.3.1 Design Coverage

The following needs to be considered and where appropriate included in the design.

a) Quality and quantity requirements of any discharge

b) How the roading stormwater design is integrated into the overall stormwater system

1 Refer TP10 for detail of Extended Detention design 2 Refer Flooding Hazard plan in District Plan and any relevant Integrated Catchment Management Plan 3 The primary system shall be designed to ensure capacity to accommodate the peak flows, without surcharge - refer Table 4-2 4 LOS Council’s Level of Service is based on developed sites for the one hour storm 5 Wetland design may allow for 50% of private system capacity working to reduce design volume required



c) The type and class of materials proposed to be used

d) System layouts and alignments including

i. Route selection

ii. Topographical and environmental aspects

iii. Easements

iv. Clearances from underground services and structures

v. Provision for future extensions

vi. Location of secondary flow paths

e) Hydraulic adequacy section 4.2.4.1

f) Where applicable location of service connections

The following documents provide guidance in the design of pipes, culverts, detention and treatment devices and open channel hydraulics:

• The New Zealand Building Code (NZBC) compliance document Clause E1 Surface Water

• Technical Publication 10 (ARC TP10), Stormwater Water Management Devices Design Guidelines Manual

• Waikato Regional Council Best Practice Guidelines for Waterway Crossings

For catchments less than 10 ha, surface water runoff using the Rational Method will be accepted. For larger catchments, or where significant storage elements (such as stormwater detention and treatment devices) are incorporated, surface water runoff should be determined using an appropriate hydrological or hydraulic computerised model. All modelling shall be carried out in a DHI product or be compatible with DHI MIKE suite.

A complete copy of the model shall be provided to Council at no charge. All underlying assumptions (such as losses, time of concentration, and catchment areas) shall be clearly stated so that a full check of calculations is possible.

4.2.3.2 Primary System Design Requirements

The land drainage system shall be capable of serving the entire catchment upstream of the subdivision and must mitigate the effect it may have on downstream waterways and adjoining areas. It shall be designed within the terms of any approved ICMP.

The runoff characteristics of upstream areas are to be based on the development that is compatible with the zoning of the land at the time of engineering design.

The means of stormwater disposal shall be capable of serving the whole of the lot. Where connection to the Council system is utilised the connection must be able to service at least the whole building and developed area available on the lot. Generally each lot will have a single stormwater connection.

a) Concentrated stormwater runoff shall not be permitted to discharge across footpaths, berms, from or to adjacent properties. Sheet flow from upstream lots or sub-catchments shall be intercepted by either the primary drainage system or the overland flow paths wherever such sheet flow may create a nuisance to downstream lots.

b) Where further subdivision upstream of the one under consideration is provided for in the District Plan or Structure Plan, the stormwater pipelines are to be constructed to the upper limits of the subdivision.



c) In all developments the preferred means of stormwater disposal shall be to adopt stormwater control measures that retain the pre-development catchment characteristics for ground soakage and runoff.

d) Where soakage, transpiration and reuse cannot fully mitigate from an increase in stormwater from a development, detention is to be provided to restrict the peak runoff from the site.

e) For the purposes of determining the increase in flow between pre and post-development reference shall be made to Section 4.2.4.4.

f) Stormwater treatment devices such as wetlands, dry detention basins, rain gardens swales and filters etc are to be landscaped with vegetative cover as set out in Section 4.2.15.5. Landscape plans shall be submitted for the approval of Council prior to planting. For treatment devices constructed in conjunction with sub-division or Land Use consents, planting shall be completed and maintained as per Table 4-25 prior to vesting the treatment device to Council.

i. At the time of submitting a design, Council will also require a draft Operations and Maintenance Manual in accordance with the requirements of Section 4.4. Prior to vestment this manual shall be finalised with any alterations discussed and agreed with Council. This includes any changes required by Waikato Regional Council for consent compliance.

ii. ‘wet pond’ type detention dams should be avoided.

g) Under no circumstances shall stormwater be led to or be permitted to enter a wastewater system.

h) Subdivision and development (including any land modification) shall ensure that surface water runoff is appropriately managed in accordance with the drainage hierarchy in Section 4.1.6.

Stormwater Pumping

Council considers that pumping of stormwater is rarely a practical option because of the need for continuity of power supply and a very conservative approach to pumping design.

Applications for pumping stormwater need to have exhausted the other available options and provide sufficient risk mitigation for pump malfunction and power outages. The Developer shall provide supporting data that clearly demonstrate that all possible alternatives have been investigated with their application.

Availability/Capacity of Council Stormwater Reticulation

Where a development will result in an increase in stormwater flow, Developers shall investigate the availability and capacity of existing Council channels (up the 1% AEP event) or reticulation (up to the relevant LOS) to ensure the proposed additional flows to be discharged to them can be accommodated. Council may request additional capacity if the proposed network is critical for the long term planning of City growth.

4.2.3.3 Secondary System Design Requirements

Secondary systems shall consist of overland flow paths to manage excess runoff that cater for events exceeding the capacity of the primary system and occasions when the primary drainage system fails.



Where possible, these secondary systems shall be located on land that is, or is proposed to become public land. If located on private land, the secondary system shall be protected by an easement and consent notice. Public safety shall be incorporated into any design.

The easement and consent notice shall:

• Cover the full extent of the secondary flow path and shall not be less than 1.5m wide

• Have the effect of preventing alteration of the ground surface and prohibit the location of structures that might impede the flow of water across the land

• Be in favour of the Council and/or the upstream lot(s) as appropriate

The easement shall be duly granted, reserved and shown on the survey plan.

Stormwater secondary flow paths shall be delineated to assist recognition and preservation of their purpose. Drawing D4.4 shows the minimum treatment required.

Additional edge treatments and hardening of the base surfaces shall be provided where applicable due to surface flow volumes and velocities.

Secondary flow on roads shall generally be limited to operating in the Low Hazard Flood Zone (Figure 4-1). Sites that do not comply with this shall be clearly identified on engineering plans.

Figure 4-1: Hamilton City Flood Hazard Classification Matrix

Secondary systems shall be designed so that erosion or land instability will not occur. Where necessary the design shall incorporate special measures to protect the land against such events.

4.2.3.4 Treatment Trains

Where appropriate the system design should incorporate a number of treatment and detention devices prior to stormwater entering a natural watercourse. Each treatment system should address the needs of the potential for contamination, detention and temperature of the stormwater.

4.2.4 Design Criteria All new stormwater systems shall be designed considering climate change adjusted design storms of at least the annual exceedance probability (AEP) set out in



Table 4-2 below unless specific approval has been obtained from Council.

Table 4-2: Design Level of Service

Level of Service

AEP (%) Rainfall Intensity

Return Period (ARI) (years)

Primary Systems

Residential Area 50 2

Industrial Area 20 5

Commercial Area, Business, CBD 10 10

Community and Major Facilities 10 10

Parks, Reserves and Open Spaces 50 2

Rural and future Urban 50 2

Transport Corridor 50 2

Secondary Systems

Local Roads 1 100

Collector Roads 1 100

Minor Arterial 1 100

Major Arterial 1 100

4.2.4.1 Stormwater Flow Estimate

The runoff coefficients shown in Table 4-3 below are to be used for the various zones and are provided as a guide for initial calculation of system requirements. More accurate investigations into appropriate return periods and runoff coefficients will be necessary for detailed design. Detailed design should involve calculating a weighted average runoff coefficient by averaging the value for individual parts of the catchment. This may be done for a representative sample area or the whole catchment. The formula for this calculation is shown in Clause 2.1 Verification Method for the ‘NZ Building Code Clause E1 Surface Water’.

Table 4-3: Runoff Coefficients

Zoning Minimum Runoff Coefficient

(C)

General Residential (flat terrain) 0.6

General Residential (slopes >5%) 0.65

Residential Medium/High Density 0.8

Industrial 0.8



Zoning Minimum Runoff Coefficient

(C)

Central City, Business 0.90

Community and Major Facilities 0.80

Future Urban 0.35

Rural 0.25

Open Space 0.35

Transport Corridor 0.8

In refining the estimate of runoff coefficients provided in Table 4-3 below the NZ Building Code Clause E1 Table 2 shall be used. The coefficients in Table 4-4 are provided as a guide.

Table 4-4: Runoff Coefficients Refined

Surface Runoff Coefficient

(C)

Runoff Coefficient

(C)

If compaction is likely during Development

Roofs 0.95

Asphaltic and Concrete Areas

0.90

Uncultivated Ground, Lawns and Playing

0.30 0.5

Cultivated Ground and Dairy Farmland

0.20 0.5

Catchments Larger than 10 ha

For larger catchments (greater than 10 Ha), or where significant storage elements are incorporated, surface water runoff should be determined using an acceptable hydrological or hydraulic model.

4.2.4.2 Time of Concentration

The time of concentration shall be determined as the ‘time of entry’ plus the ‘time of flow’ from the furthest part of the whole catchment to the point of discharge.

Time of entry to the system shall be calculated from the Overland Flow Graph in



Figure 4-2, or an equivalent published graph or the formula from which it was derived.

Time of flow can be calculated from the flow velocity in pipes and channels.

Note: since time of concentration is not known initially, an iterative type solution is necessary with time of concentration recalculated from the catchment flow calculation.



Figure 4-2: Overland Flow Graph



4.2.4.3 Design Rainfall

Hamilton City’s rainfall design data is derived from the Ruakura rainfall gauge.

Note: The HIRDS rainfall design tool tends to provide different data for Hamilton City due to the averaging of rainfall gauges; HIRDS derived data is therefore not an acceptable alternative for use within Hamilton City.

Table 4-5: Current Rainfall

Ruakura Rainfall Intensity (mm/hr)

ARI 10m 20m 30m 60m 2h 6h 12h 24h 48h 72h

2 60.9 43.7 35.1 23.3 14.5 7.1 4.5 2.8 1.6 1.2

5 79.5 59.0 48.3 32.6 20.0 9.2 5.8 3.6 2.2 1.5

10 91.9 69.1 47.1 38.7 23.6 10.6 5.7 4.1 2.5 1.8

50 119.1 91.3 76.4 52.2 31.5 13.6 8.6 5.3 3.2 2.3

100 130.6 100.7 84.6 57.9 34.9 14.9 9.4 5.8 3.5 2.5

Ruakura Rainfall Depth (mm)

ARI 10m 20m 30m 60m 2h 6h 12h 24h 48h 72h

2 10.4 14.9 17.6 22.3 27.6 40.8 53.3 63.8 75.7 82.3

5 13.9 20.7 24.8 30.8 36.7 50.7 59.7 81.6 98.4 105.7

10 16.2 45.5 29.6 36.4 42.7 57.3 77.5 93.3 113.4 121.1

50 21.4 32.9 40.1 48.7 56.0 71.8 98.8 119.2 146.4 155.2

100 23.6 36.5 44.6 54.0 61.6 77.9 107.7 130.2 160.3 169.6

The current rainfall pattern is used to determine detention requirements for infill developments where existing connections generate ‘existing use rights’ and also for temporary works where climate change rainfall is not relevant.

In May 2008 Council adopted the following Climate Change adjusted rainfall data for use in determining stormwater flows. This data provides for an IPCC A1B mid-low emissions scenario with 2.08 degrees Celsius average temperature rise by 2100, and shall be used for determining post-development flows.



Table 4-6: Adjusted Rainfall Data – 2.08 degrees Celsius

Ruakura Rainfall Intensity (mm/hr) Incorporating 2.08 degrees Celsius Climate Change

ARI 5m 10m 20m 30m 60m 2h 6h 12h 24h 48h 72h

2 9. 71.0 50.6 40.4 26.5 16.4 7.9 5.0 3.0 1.8 1.3

5 116.1 92.7 68.4 55.7 37.4 22.8 10.4 6.5 4.0 2.4 1.7

10 133.0 107.2 80.3 66.1 44.7 27.1 12.1 7.6 4.7 2.8 2.0

20 149.9 121.0 91.7 76.1 51.7 31.3 13.7 8.6 5.3 3.2 2.3

50 172.0 138.9 106.5 89.1 60.9 36.7 15.9 10.0 6.2 3.8 2.6

100 182.7 152.3 117.5 98.7 67.5 40.7 17.4 10.9 6.8 4.1 2.9

Ruakura Rainfall Depth (mm) Incorporating 2.08 degrees Celsius Climate Change

ARI 5m 10m 20m 30m 60m 2h 6h 12h 24h 48h 72h

2 7.7 11.8 16.9 30.2 26.5 32.7 47.3 59.9 72.2 84.9 91.1

5 9.7 15.5 22.8 27.9 37.4 45.6 62.2 78.5 95.0 114.5 121.2

10 11.1 17.9 26.8 33.1 44.7 54.3 72.3 91.3 112.1 135.2 142.3

20 12.5 20.2 30.6 38.1 51.7 62.5 82.4 103.7 129.9 154.2 165.0

50 14.3 23.2 35.5 44.6 60.9 73.5 95.2 120.4 148.9 180.3 189.8

100 15.2 25.4 39.2 49.3 67.5 81.4 104.3 131.0 162.9 198.2 208.3

The following data provides for an IPCC A1F1 mid-high emissions scenario with 3.0 degrees Celsius average temperature rise by 2100. The flooding consequences of this scenario shall be considered and where the resulting flooding level exceeds the finished floor level (FFL) set on a property, the FFL shall be raised to 150mm above that flooding level.

Note: The Proposed Regional Policy Statement Decisions (November 2012) Section 4.1.14(a) refers to a 2.1 degrees Celsius average temperature rise by 2090. This section has not yet been updated to reflect this change.

Table 4-7: Adjusted Rainfall Data – 3.0 degrees Celsius

Ruakura Rainfall Intensity (mm/hr) Incorporating 3.0 degrees Celsius Climate Change

ARI 5m 10m 20m 30m 60m 2h 6h 12h 24h 48h 72h

2 98.8 75.5 53.7 42.7 28.0 17.2 8.2 5.2 3.1 1.8 1.3

5 123.4 98.6 72.6 59.0 39.5 24.0 10.9 6.9 4.1 2.5 1.8

10 141.4 114.0 85.3 70.1 47.3 28.7 12.7 8.0 4.9 3.0 2.1

20 159.3 128.6 97.5 80.8 54.9 33.2 14.5 9.1 5.6 3.4 2.4

50 182.9 147.7 113.2 94.7 64.7 39.1 16.9 10.7 6.6 4.0 2.8

100 194.2 161.9 124.9 104.9 71.8 43.3 18.5 11.6 7.2 4.4 3.1

Ruakura Rainfall Depth (mm) Incorporating 3.0 degrees Celsius Climate Change

ARI 5m 10m 20m 30m 60m 2h 6h 12h 24h 48h 72h



2 8.2 12.6 17.9 21.3 28.0 34.4 49.4 62.3 74.8 87.7 93.9

5 10.3 16.4 24.2 29.5 39.5 48.0 65.3 82.3 99.3 119.2 126.0

10 11.8 19.0 28.4 35.1 47.3 57.4 76.3 96.1 117.9 142.0 149.1

20 13.3 21.4 32.5 40.4 54.9 66.3 87.3 109.7 134.2 163.0 174.2

50 15.2 24.6 37.7 47.4 64.7 78.1 101.0 128.0 158.3 191.7 201.8

100 16.2 27.0 41.6 52.5 71.8 86.6 110.9 139.9 173.2 210.7 221.4

4.2.4.4 Design Storm

In any greenfield development where detention storage is present or will be required, the stormwater design shall be based on hydraulic modelling using 24-hour nested design storms as tabulated below.

Table 4-8: Present Climate – For Assessing Pre-Development Flows

Table 4-9: Incorporating 2.08 degrees Celsius Climate Change – For Assessing Post – Development Flows

Depthmm

Intensitymm/h

Depthmm

Intensitymm/h

Depthmm

Intensitymm/h

Depthmm

Intensitymm/h

Depthmm

Intensitymm/h

Depthmm

Intensitymm/h

0:00 360 5.9 1.0 7.7 1.3 9.4 1.6 10.2 1.7 12.2 2.0 13.7 2.36:00 180 5.9 2.0 7.4 2.5 8.5 2.8 9.3 3.1 10.8 3.6 11.5 3.89:00 120 6.8 3.4 7.6 3.8 8.1 4.0 8.7 4.4 9.3 4.7 9.8 4.9

11:00 30 2.9 5.7 3.7 7.4 4.3 8.5 4.7 9.4 5.4 10.8 6.0 11.911:30 15 2.9 11.5 4.2 16.9 5.1 20.3 5.9 23.7 7.0 28.0 7.8 31.211:45 5 1.5 17.9 2.2 26.9 2.8 33.1 3.2 38.9 3.9 46.6 4.4 52.411:50 5 2.2 26.5 3.2 38.5 3.9 46.3 4.5 53.9 5.3 63.5 5.9 70.811:55 10 10.2 60.9 13.3 79.5 15.3 91.9 17.3 103.7 19.9 119.1 21.8 130.612:05 5 2.2 26.5 3.2 38.5 3.9 46.3 4.5 53.9 5.3 63.5 5.9 70.812:10 5 1.5 17.9 2.2 26.9 2.8 33.1 3.2 38.9 3.9 46.6 4.4 52.412:15 15 2.9 11.5 4.2 16.9 5.1 20.3 5.9 23.7 7.0 28.0 7.8 31.212:30 30 2.9 5.7 3.7 7.4 4.3 8.5 4.7 9.4 5.4 10.8 6.0 11.913:00 120 6.8 3.4 7.6 3.8 8.1 4.0 8.7 4.4 9.3 4.7 9.8 4.915:00 180 5.9 2.0 7.4 2.5 8.5 2.8 9.3 3.1 10.8 3.6 11.5 3.818:00 360 5.9 1.0 7.7 1.3 9.4 1.6 10.2 1.7 12.2 2.0 13.7 2.324:00

66.2 85.4 99.1 110.4 127.7 139.7

2-year ARI 5-year ARI 10-year ARI 50-year ARI 100-year ARIRuakura design storms, 1947-2006 climate

20-year ARITime interval

min

Start time

hh:mm

Depthmm

Intensitymm/h

Depthmm

Intensitymm/h

Depthmm

Intensitymm/h

Depthmm

Intensitymm/h

Depthmm

Intensitymm/h

Depthmm

Intensitymm/h

0:00 360 6.1 1.0 8.3 1.4 10.4 1.7 11.6 1.9 14.3 2.4 16.0 2.76:00 180 6.3 2.1 8.2 2.7 9.5 3.2 10.6 3.5 12.6 4.2 13.4 4.59:00 120 7.3 3.6 8.3 4.2 9.0 4.5 9.9 5.0 10.8 5.4 11.4 5.7

11:00 30 3.1 6.2 4.1 8.2 4.8 9.6 5.4 10.8 6.3 12.6 6.9 13.911:30 15 3.2 12.7 4.8 19.1 5.8 23.2 6.8 27.4 8.2 32.7 9.1 36.411:45 5 1.7 19.9 2.5 30.3 3.1 37.8 3.7 44.9 4.5 54.4 5.1 61.111:50 5 2.5 30.2 3.7 44.2 4.5 53.4 5.2 62.5 6.2 74.1 6.9 82.611:55 10 11.8 71.0 15.5 92.7 17.9 107.2 20.2 121.0 23.2 138.9 25.4 152.312:05 5 2.5 30.2 3.7 44.2 4.5 53.4 5.2 62.5 6.2 74.1 6.9 82.612:10 5 1.7 19.9 2.5 30.3 3.1 37.8 3.7 44.9 4.5 54.4 5.1 61.112:15 15 3.2 12.7 4.8 19.1 5.8 23.2 6.8 27.4 8.2 32.7 9.1 36.412:30 30 3.1 6.2 4.1 8.2 4.8 9.6 5.4 10.8 6.3 12.6 6.9 13.913:00 120 7.3 3.6 8.3 4.2 9.0 4.5 9.9 5.0 10.8 5.4 11.4 5.715:00 180 6.3 2.1 8.2 2.7 9.5 3.2 10.6 3.5 12.6 4.2 13.4 4.518:00 360 6.1 1.0 8.3 1.4 10.4 1.7 11.6 1.9 14.3 2.4 16.0 2.724:00

72.2 95.0 112.1 126.9 148.9 162.9

Start time

hh:mm

Time interval

min

2-year ARI 5-year ARI 10-year ARI 50-year ARI 100-year ARIRuakura design storms, incorporating 2.08 degrees Celsius climate change

20-year ARI



Table 4-10: Incorporating 3.0 degrees Celsius climate change – Consider the Flooding Consequences of This Scenario

Table 4-11: Infill Development Stormwater Level of Service, Return Period and Runoff Coefficient

Zoning Industrial/ Major Facilities

Business/ Community

Residential Zoning

Rainfall intensity return period for piped discharge - Council level of service

20% 10% 50% 50%

Rainfall intensity return period for total site system including secondary flows

50 mm/hr 50 mm/hr See Tables in Section 4.2.4.4

See Tables in Section

4.2.4.4

Runoff Coefficient C 0.9 0.9 0.75 0.5

The above runoff coefficients are for peak flow rate and shall be modified for slope as discussed in NZ Building Code Clause E1.

4.2.4.5 Volumetric Runoff Coefficients

Volumetric runoff coefficients as per Table 4-12 below shall be used in hydraulic modelling to allow for infiltration losses. The volumetric runoff coefficient shall be as given in Table 4-12 or based on the NZ Building Code Clause E1 coefficients referred with adjustments as follows.

Table 4-12: Volumetric Runoff Coefficients

Adjusted from the NZ Building Code E1 coefficients given in Clause 4.6.1.2

50 – 20% AEP 10 – 5% AEP 2 – 1% AEP

Roofs 0.99 0.99 0.99 Asphaltic and concrete areas

0.95 0.95 0.95

Uncultivated ground, lawns and playing fields

0.34 0.36 0.38

Cultivated ground and dairy farmland

0.24 0.26 0.28

Depthmm

Intensitymm/h

Depthmm

Intensitymm/h

Depthmm

Intensitymm/h

Depthmm

Intensitymm/h

Depthmm

Intensitymm/h

Depthmm

Intensitymm/h

0:00 360 6.2 1.0 8.5 1.4 10.9 1.8 12.3 2.0 15.2 2.5 17.0 2.86:00 180 6.5 2.2 8.5 2.8 9.9 3.3 11.2 3.7 13.4 4.5 14.2 4.79:00 120 7.5 3.7 8.6 4.3 9.4 4.7 10.5 5.2 11.5 5.8 12.2 6.1

11:00 30 3.2 6.4 4.2 8.5 5.1 10.1 5.7 11.4 6.7 13.4 7.4 14.811:30 15 3.3 13.3 5.0 20.1 6.1 24.5 7.2 29.0 8.7 34.7 9.7 38.711:45 5 1.7 20.7 2.7 31.8 3.3 39.8 4.0 47.5 4.8 57.8 5.4 65.011:50 5 2.7 31.8 3.9 46.7 4.7 56.6 5.5 66.4 6.6 78.7 7.3 87.811:55 10 12.6 75.5 16.4 98.6 19.0 114.0 21.4 128.6 24.6 147.7 27.0 161.912:05 5 2.7 31.8 3.9 46.7 4.7 56.6 5.5 66.4 6.6 78.7 7.3 87.812:10 5 1.7 20.7 2.7 31.8 3.3 39.8 4.0 47.5 4.8 57.8 5.4 65.012:15 15 3.3 13.3 5.0 20.1 6.1 24.5 7.2 29.0 8.7 34.7 9.7 38.712:30 30 3.2 6.4 4.2 8.5 5.1 10.1 5.7 11.4 6.7 13.4 7.4 14.813:00 120 7.5 3.7 8.6 4.3 9.4 4.7 10.5 5.2 11.5 5.8 12.2 6.115:00 180 6.5 2.2 8.5 2.8 9.9 3.3 11.2 3.7 13.4 4.5 14.2 4.718:00 360 6.2 1.0 8.5 1.4 10.9 1.8 12.3 2.0 15.2 2.5 17.0 2.824:00

74.8 99.3 117.9 134.2 158.3 173.2

Ruakura design storms, incorporating 3.0 degrees Celsius climate changeStart time

hh:mm

Time interval

min

2-year ARI 5-year ARI 10-year ARI 20-year ARI 50-year ARI 100-year ARI



The above coefficients shall be adjusted for ground slope in accordance with NZ Building Code Clause E1, Table 2.

4.2.4.6 Energy Loss through Structure

Energy loss is expressed as velocity head:

Energy loss:

He = kV2/2g

where k is the entrance loss coefficient and V is velocity.

The entrance loss coefficient table and energy loss coefficient graph in NZ Building Code Clause E1/VM1 provide k values for flow through inlets and access chambers respectively.

For bends, see Table 4-13: Loss Coefficients for Bends.

4.2.4.7 Determination of Water Surface Profiles

Stormwater systems shall be designed by calculating or computer modelling backwater profiles from an appropriate outfall water level. On steep gradients both inlet control and hydraulic grade line analysis shall be used and the more severe relevant condition adopted for design purposes. For pipe networks at manholes and other nodes, water levels computed at design flow shall not exceed finished ground level while allowing existing and future connections to function satisfactorily.

In principle, each step in the determination of a water surface profile involves calculating a water level upstream (h2) for a given value of discharge and a given start water level downstream (h1).

This can he represented as:

h2 + V22/2g = h1 + V 12/2g + Hf + He

where V is velocity,

Hf is head loss due to boundary resistance within the reach (for pipes, unit head loss is read from Manning’s flow charts),

He is head loss within the reach due to changes in cross section and alignment (refer Table 4-13 for loss coefficients).

Table 4-13: Loss Coefficients for Bends

Bends K

MH properly benched with radius of bend

1.5 x pipe diameter 0.5 to 1.0

Bend angle

90° 0.90

45° 0.60

22.5° 0.25



4.2.4.8 Minimum Pipe Diameters

4.2.4.9 Piped Reticulation System Minimum Requirements

a) Irrespective of other requirements, the minimum pipe size for a public wastewater pipe shall be not less than 150DN and a lateral connection not less than 100DN.

b) In no circumstances shall the pipe size be reduced on any downstream section.

Table 4-14: Minimum Pipe Sizes

Situation Minimum Size (mm)

Single catchpit lead 225

Double catchpit lead 300

Single dwelling 100

2 - 3 dwellings 150

Stormwater Network Pipe 150

4.2.4.10 Minimum Gradients and Flow Velocities in Pipes

Pipe gradients should be at a grade that prevents silt deposition. The minimum velocity should be at least 0.6m/s at a flow of half the 50% AEP design flow. For velocities greater than 3.0m/s specific design to resist erosion is required.

4.2.4.11 Freeboard

All buildings must comply with the following minimum freeboard heights which are additional to the top water flood level of the 1% Annual Exceedance Probability (AEP) design storm.

Table 4-15: Flooding Freeboard requirements

A: Catchment Area B: Ponding Depth C: Flow Velocity

ha mm mm mm m/s mm 0.5< 150 <100 150 <0.5 150 0.5 175 100-249# 225# 0.5-.99 300 1 200 250-499# 350# 1.0-1.49 425 2 225 500-749# 475# 1.5-1.99 550 3 250 750-999 600 2+ 675 4 275 1000+ 675

5 300

# on site rather than adjacent to building - if touching building then 500 mm minimum freeboard to FFL as per Building Act

6 325

7 350

The required freeboard to Finished Floor Level for habitable dwellings and attached garages is the highest value determined from tables A - C above.

8 375 9 400

10 425

11 450

Commercial and industrial buildings FFL may be



12 475

200mm lower, non-habitable residential buildings and detached garages FFL may be 300mm lower, but in no case shall any FFL be located lower that the calculated flood level plus 150mm.

13 500 14 525

15 550 16 575 17 600 18 625 19 650 20+ 675

Freeboard for culverts conveying secondary flow paths under roads shall comply with the minimum requirements shown in Table 4-16 below.

Table 4-16: Road Flooding Freeboard Requirements

Road Class Minimum Freeboard Height (m)

Local 0.5

Collector 0.75

Arterial 1.0

4.2.4.12 Soakage and Detention Calculations

Calculations of soakage and detention requirements need to identify the most severe combination of rainfall and soakage/discharge for all storm durations. This shall then be used to determine the size of the soakage/detention facility. Council has developed standard spreadsheets to help determine the level of soakage and/or detention required to reduce the rate of discharge to the acceptable level. Reference should be made to the design templates appended in this section.

4.2.5 Watercourses Natural watercourses are expected to be retained.

Refer to the relevant District Plan, in particular the Environmental Protection Overlay (Operative District Plan) and the Hazard Layers and Significant Natural Areas (Proposed District Plan) to ensure all planning requirements are incorporated into any design

The extent of stream drainage work shall be designed to achieve a satisfactory solution recognising:

• Community flood protection

• Bank stability

• The retention of the natural topography and ecological values

• Maintenance

• Hydraulic and safety considerations

• Downstream effects of the work



4.2.5.1 Constructed Water Courses

Constructed watercourses (open drains) may be piped if there are valid engineering or design considerations, ecological impacts have been considered and Regional Council approval is obtained where necessary. The engineering plans should be noted accordingly.

Where waterways are to be incorporated in the stormwater system, they shall be located within a reserve of sufficient width to contain the full design storm flow from a 1% AEP event with a minimum freeboard as per Section 4.2.4.11.

Grass berms in reserves shall have a maximum side slope of 1 in 5 and additionally include a vehicular access berm for maintenance purposes.

Planted riparian margins shall be provided each side of the waterway and shall consider maximisation of bank stability and public safety, refer landscaping section for further information.

All channel infrastructure shall include protection against scour and erosion of the stream banks and stream bed using biotechnical treatments where feasible.

lf the constructed watercourse is to be in private property, discussions will need to be held with Council to determine responsibility of maintenance. At minimum the constructed watercourse shall be protected by an easement and constructed in compliance with Drawing D4.4, or an accepted equivalent.

4.2.5.2 Natural Open Stream Systems

Where natural open stream systems or formed channels are to be incorporated in the stormwater drainage system they shall generally be located within a drainage reserve of sufficient width to contain the overall system design storm flow.

a) It must be demonstrated that the open drain system:

i. Can be used where it is in keeping with the existing drainage network

ii. Is the only option available that will work hydraulically

iii. Provides at least the same capacity as an equivalent piped system

iv. Where ash or clay soils are present, the maximum velocity in an unlined open drain shall be 0.5m/sec. When this is unable to occur, an appropriate channel lining will be required

b) Drainage reserves shall have maximum and minimum slopes of 1:5 and 1:50 respectively. When access for maintenance is required, access provisions shall also include:

i. A 4m wide berm that is accessible by an 8.2 tonne axle weight vehicle for its entire length.

ii. Access from public carriageways

c) To encourage the best use of the open stream systems the drainage reserve shall, where possible, be linked with other reserves and open spaces to accommodate off road pedestrian and cycle access. Access points for public use and maintenance shall be provided at regular intervals along the system together with footpath and pedestrian bridges, as may be defined in the resource consent.

d) The flow characteristics of natural open stream systems shall:



i. Be based on the likely long term stream condition in terms of density of vegetation

ii. Be cleared of all unsuitable plant growth and replanted to a landscape design approved by Council

iii. Take account of the possibility of blockage under all peak flood conditions

iv. Include protection of the low flow channel against scour and erosion of the stream bed where necessary

v. Not be changed by the discharge of stormwater resulting from development or a new discharge to the stream

vi. Be designed to avoid erosion of the stream banks

e) Catchment or detention factors that may lead to an increase in the temperature of the stormwater (e.g. large sealed areas) shall be mitigated

Where a section of watercourse is to be piped (e.g. for crossings), reference shall be made to Section 4.2.11.

4.2.6 Piped System Layout Refer Wastewater Section.

4.2.7 Manholes Refer Wastewater Section.

4.2.7.1 Manhole Connections

Open cascade is permitted into manholes over 2.0m in depth and for pipes up to and including 300mm diameter providing the steps are clear of any cascade. Other situations may be considered and require Council approval (refer to Drawing D4.1 – D4.3).

Local pipelines connecting above design water level may do so at any angle.

4.2.8 Connections 4.2.8.1 General

The lateral connection should be designed to suit the existing situation and any future development.

For all connections to an open watercourse, resource consents from Waikato Regional Council will be required.

4.2.8.2 Design Requirement

The following design requirements shall be met:

a) Stormwater management as per hierarchy in Section 4.1.6

b) Where no other option is available, a ‘bubble-up’ discharge to the kerb and channel will be required in the residential high density, commercial and industrial areas. The less expensive Kerb and Channel connections will only be approved in place of 'bubble-up' outlets in normal residential zones where, there is a suitable kerb profile and, the Kerb and Channel can be installed at least 1.0m clear of any vehicle crossing.



c) If connecting to a Council pipe, the standard depth of a stormwater connection at the boundary is 1.2m (allowable range 0.9 m - 1.5 m).

d) To determine whether a connection can clearly serve the whole developable area of the lot, the invert level should be calculated at grade 1:80 from the Council pipeline invert to the lot boundary and then at 1:100 to the furthest point within the lot. If after allowing for the pipeline diameter, the depth of soil cover over the pipeline is less than 0.5m the final design will need to be to the satisfaction of Council's Building Unit.

e) Existing connections, not documented on Council records may be reused subject to confirmation of existing construction suitability and as-built information is provided to update Council's records.

f) Detention of stormwater prior to release to the Council network is required. Early consultation is encouraged with Council staff to seek a suitable solution at the outset of the development.

g) As a guide only, a simplified assumption for infill residential development where the extension of Council services or creation of overland flow paths suitable to cater for the 100-year storm event through a neighbouring property is difficult, the design may be based on Table 4-17 below.

h) Minimum size for connections is as per Table 4-14 above.

i) All connections, which are to be made directly to the line, shall be designed using a factory manufactured ‘wye’ or ‘London Junction’ and shall be watertight.

Table 4-17: Rainfall Intensity Return Period (ARI) for Infill Residential Development

Secondary Flow Path Scenario ARI for System Design

Falls towards public road >2% 2 year

Flat (+/– 2%) 10 year

Falls away from public road >2% 50 year



Note: Private drainage is shown as indicative only, refer Building Act / Code for requirements

Figure 4-3: Connections for Single Development or Subdivision

4.2.8.3 Services in Accessways, Access Lots, or Rights of Ways

The following should be considered when preparing design:

a) Where drainage is to a piped network the following figure provides a suggested layout

b) Council will adopt the stormwater network in the right-of-way where it services 2 or more properties. All private drainage reticulation that has been upgraded in accordance with this standard shall be declared public at the point where it crosses a boundary once as-built information has been recorded by Council

Soak-holes

Privately Owned Soak-hole

PropertyBoundaries

Stormwater Main

P

Service Pipe

Single Property, Single Connection, Outside Property

PropertyBoundaries

Stormwate

PropertyBoundaries

Service Pipe

Single Property, Single Connection, Inside Property

Point of Discharge at the connection

stub, see D4.4

Stormwater Main

Subdivision, Two Connections, Inside Property

Old service pipe de-commissioned, as services cannot

run underneath buildings.

New service pipe.

Point of Discharge at the serviced

properties boundary

Point of Discharge at the connection

stub, see D4.4

HCC Ownership Private Ownership



Note: Private drainage is shown as indicative only, refer Building Act/Code for requirements

Figure 4-4: Connections to a right of way

4.2.8.4 Multi-Unit Properties

For multiple occupancy situations, service of the whole property shall be achieved by providing a single point of connection to the Council stormwater system where applicable. 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 will be considered to be private.

• Pipe Size and material shall be determined by site-specific design in accordance with Compliance Document for the NZ Building Code Clause E1 Surface Water or this document

• A manhole/chamber is to be provided just within the lot boundary

Stormwater Main

Privately Owned Soak-hole if

possibleRight of Way

Point of Discharge at the serviced

properties boundaries

Manhole required for clearing of

blockages.




Note: Private drainage is shown as indicative only, refer Building Act / Code for requirements

Figure 4-5: Connections for Multi Unit Developments

4.2.8.5 Ramped Risers

Unless required otherwise by Council, a ramped riser shall be constructed to bring the connection to within 0.9m - 1.5m of ground level, or to such depth that will permit a gravity connection to service the whole lot. Ramped risers shall be constructed as shown in Drawing D4.4.

4.2.8.6 Connections to Deep Lines

Where an existing or proposed main is more than 5m deep, or where required by the ground conditions, a manhole will need to be constructed on the deep line and a shallower connection laid from the manhole.

4.2.9 Catchpits The design and construction of catchpits shall be undertaken so that:

a) Catchpits are capable of capturing and retaining the majority of gross pollutants, and floatable contaminants including oil and grease

b) Catchpits shall be accurately positioned so that the grate and kerb block fit neatly into the kerb and channel. Rectangular pits shall be oriented with the longer side parallel to the kerb

c) Catchpit leads shall be of the size and material detailed on the plans or specification and shall discharge where detailed

d) Catchpit leads not more than 300 mm diameter and not more than 20 m in length may be saddled on to pipes 600 mm diameter and larger, without manholes

e) Technology regarding pre-treatment devices within catchpits is continuously evolving. Where devices are required, consultation with Council is required to ensure the proposed device meets with Councils operations and maintenance requirements. Any

Single Lot

Stormwater Main

Point of Discharge at Boundary

Stormwater Catchpit

If greater than 120m, then

another manhole is required.

Manhole required for clearing of

blockages.




alternative designs of stormwater catchpits shall be capable of capturing and retaining the majority of gross pollutants and floatable contaminants such as oil and grease

f) Drawings D4.6 – D4.10 provide details for the construction of catchpits

g) Refer Approved Materials Section 9 for list of permitted precast components

4.2.10 Outlets and Inlets Approved structures shall be constructed at the inlets and outlets of pipelines. Alternative proprietary structures are permissible subject to site specific approval by Council.

4.2.10.1 Waikato River Outfalls

Outfalls to the Waikato River need to be reviewed by both Waikato-Tainui and Mighty River Power in conjunction with seeking approval from Council and the Waikato Regional Council. Outlets should not be located in sites of recognised cultural or historical significance.

Note relevant documents:

• The Mighty River Power/Hamilton City Council Agreement

• The Central Waikato River Stability Management Strategy

• Waikato-Tainui Raupatu Claims (Waikato River) Settlement Act 2010

• HCC River Precinct Study 2012.

Design of the outfall should allow 30 mm/yr for bed degradation. The level of bed degradation will be reviewed periodically.

The daily permitted water level variation at the Bridge Street bridge from 2001 – 2008 is given below:

Minimum recorded level 2001 – 2008 11.53m

Maximum recorded level (Feb 2004 Flood) 16.24m

4.2.10.2 Outlet Design (Streams and Rivers)

Outlet designs shall incorporate the following:

a) Alignment with an approved ICMP

b) Fitness for purpose over the design life

c) River level and flows

d) River bank erosion to 0.5m below minimum river level

e) Energy dissipation and the design shall ensure non-scouring velocities at the point of discharge

f) Seasonal variations in power generation

g) Extending outlet works below the river surface

h) Developing a consistent design criteria for outlet works taking into account public safety requirements, natural character of the surrounds, amenity and aesthetics of the river

i) Appropriate planting of eco-sourced indigenous species where required

j) Retaining remnant areas of indigenous riverbank vegetation



k) For outlets the design shall ensure non-scouring velocities at the point of discharge. Acceptable outlet velocities will depend on soil conditions, but should not exceed 2m/s without specific provision for energy dissipation and velocity reduction

4.2.10.3 Inlet Design

Screens are required where flow from open drains, detention and treatment systems enters into a piped network (excluding culverts). Specific design is required to meet the requirements of the site and public safety issues.

4.2.11 Culverts A culvert is a pipe that carries water from one side of a road, driveway, railway or other obstruction to the other. Culverts will be buried at some depth below the surface and aligned so as to permit the passage of water with minimum obstruction to the watercourse. Culverts are generally short in length and open at both ends and often must withstand substantial traffic loads. While the installation does not require a large quantity of pipe, the installed drainage structure is extremely important to the overall road/drainage interface.

When boxes/pipes/arches or culverts are placed side-by-side to create a width of greater than 6.0m, the culvert is defined as a bridge culvert – these shall be designed in accordance with the TNZA Bridge Manual SP/M/022 , Waikato Regional Council document ‘Best Practice Guidelines for Waterway Crossings’ for fish passage and Transportation section 3.2.28.1.

Where possible ‘arch’ culverts shall be the preferred culvert of choice to retain stream width and natural bed material. Where arch culverts cannot be used, consideration shall be given to design details that allow appropriate conveyance of water flow and unimpeded fish passage. The design shall optimise low velocity zones, minimal turbulence, light, longitudinal bed gradient, bed level that is not raised. The design shall minimise upstream flooding, blockages and scouring.

If culvert design results in upstream ponding of more than 3.0 m it is considered a ‘dam’.

Waikato Regional Plan rules also stipulate design and consent requirements for the number of hectares in a catchment being drained through a culvert.

It is usual for resource consents to require that culvert construction be accompanied by sediment control measures as set out in an Erosion and Sediment Control Plan. Refer to Waikato Regional Council’s Erosion and Sedimentation Guidelines.

4.2.11.1 Catchment Parameters

In the absence of an approved ICMP or CMP, the following information shall be obtained for crossing design:

a) Catchment area to drain through the culvert

b) Topography

c) Land use description and potential for land use change

d) Maximum channel and catchment length

e) Change in elevation over maximum channel length

f) Catchment slope and orientation

g) Average slope over maximum channel length

h) Existing channels both upstream and downstream



4.2.11.2 Design Storm

Culverts shall be designed as a minimum to accommodate storms as per Table 4-18 below. The design shall not cause any increase in upstream water levels that will cause flooding on neighbouring properties.

Table 4-18: Culvert Design Storms

Design case AEP storm to pass without surcharge (design flow)

AEP storm not overtopping structure (peak flow)

Driveway or private accessway 50% 20%

Pedestrian or cycleway walk 20% 10%

Local or Collector Road 20% 5%

Arterial roads and railways 5% 1%

4.2.11.3 General Design Criteria

The following general design criteria shall be applied to culverts.

a) The culvert must never be more than half full at average flow

b) Culverts shall accommodate the full width of the stream at average flow

c) The effects of inlet and tailwater controls shall be considered and mitigated

d) Culvert diameter shall be selected that design peak flood flow can pass without the culvert embankment being overtopped. This reduces the likelihood of the embankment failing due to scour

e) Culverts shall be designed to safely overtop without causing structural failure

f) Culverts shall be sized so that the largest bed material in the stream can pass either through or over the culvert

g) Where flows are typically concentrated in circular barrel culverts, the culvert diameter shall be larger than the stream width at average flow. A rule of thumb is 1.2 x channel width + 0.5m

h) Ponding behind the culvert embankment should not exceed 1.0m above the soffit, unless high water velocities are likely to cause scour around the culvert entrance and exit

i) The distance between the invert of the culvert pipe and the waterway bed level should be 20% of the culvert diameter

j) To protect against turbulence and erosion, all culverts shall be provided with adequate wingwalls, headwalls, aprons, scour protection, removable debris traps or pits to prevent scouring or blocking. Suitable riparian planting shall be undertaken

k) Culverts under fills shall be of suitable capacity to cope with the design storm with no surcharge at the inlet, unless the fill is part of a stormwater detention device or has been designed to act in surcharge. Special consideration shall be given to the effects of surcharging or blocking of culverts under fill (e.g. anti-seep collars)

l) The culverts inlet and outlet will be flush with the headwall



m) Culverts shall be designed so that they are placed on a straight section of channel where the channel gradient is lowest

n) Spillways shall be provided to cater for the overtopping scenario when flows exceed the design flow

o) Spillways shall be located in undisturbed ground and be grassed to reduce potential for scour

p) Spillway sides may require armouring to prevent erosion

q) To reduce potential for excessive turbulent flow which can cause downstream erosion, the design shall incorporate baffles or rocks, where the culvert does not have a natural stream bed. The design of this feature shall reduce the exiting flow to that of the receiving water

r) Freeboard shall be provided as described in Section 4.2.4.11

4.2.11.4 Fish Passage

Fish passage through culverts shall always be maintained. This is achieved by ensuring that the invert level is set below the stream bed level and the outlet is flooded at all times.

The Waikato Regional Council shall be consulted to determine ecological value of the waterway. In some cases, fish barriers will be desired because of their ability to prevent migration of pest fish.

Note: it may be a requirement of WRC that construction shall avoid spring and early summer.

If a waterway is reduced, the velocity along the banks at normal flow should be maintained at less than 0.3m/s to allow for passage of indigenous fish and trout.

Where multi-barrel circular culverts are to be used for wide channels that have low flows but occasional high flow events, consideration shall be given to setting each culvert at a different level to allow base flows and ensure appropriate waterway area at all flows.

4.2.12 Weirs Any weirs proposed on Council managed drains shall be specifically designed for the situation considering any ICMP requirements, hydraulic design, fish pass and access for maintenance requirements. Early consultation with Council staff is encouraged.

4.2.13 Subsoil Drains Subsoil drains are installed to control groundwater levels.

Perforated or slotted pipe used under all areas subject to vehicular traffic loads shall comply with NZTA specification F/2 and NZTA F/2 notes. The design for subsoil drains shall include regular inspection and flushing points.

In the absence of any other more appropriate criterion the design flow for subsoil systems shall be based on a standard of 1mm/h (2.78 L/s/ha).

Subsoil drainages servicing private property will not be adopted by Council.



4.2.14 Soakage Devices Soakage devices such as soak pits and soak holes, filter strips, infiltration trenches and basins, permeable paving, green roofs, and tree pits shall be considered for managing stormwater from roofs, parking areas, and on occasion roads.

The ability of the ground to accept stormwater can vary enormously within soakage areas, even within individual properties. Because of this, at least one percolation test will normally be required for every soakage device that is constructed and this should be done where the soakage device is likely to be placed.

Exceptions to the above expectations for testing are:

• Extensions to car parking or paving of less than 50m2 may use a rock filled trench along the lower edge of dimensions 0.5m wide and 0.5m deep

• Soakage device for an impervious area less than 40m2 can use nominal soak holes for Hamilton as described in Soak up your Stormwater which is available at

http://www.hamilton.co.nz/our-services/building-consents-and-information/Documents/soak%20up%20your%20stormwater.pdf.

Note: larger areas may not use multiples of these nominal designs.

Generally within Hamilton, soakage (with storage) will be expected to be utilised where soakage results are determined as per Table 4-19 below.

Table 4-19: Soakage Thresholds

Determination Method Soakage threshold

Building Code E1 Method > 150 mm/hr

Cambridge North Method > 1.0 L/m2/min

Horslev Method > 1.0 x 10-5 m/s

Soakage is allowed in soils with lower soakage however specific engineering design is required and for soils with low permeability rates, tests must be carried out by an IANZ (International Accreditation New Zealand) laboratory (refer IANZ’s website for details www.ianz.govt.nz).

Specific matters to be considered in soakage system design include

a) Capacity adequate for a 10% AEP event, maximum potential impermeable area and located in such a way to maximise the collection of site runoff

b) Soakage devices must not be located within a 10% AEP storm flood plain, and if possible should be located outside the 2% AEP flood plain. They should be located away from overland flow paths

c) Rate of soakage determined through a soakage test with an appropriate reduction factor (at least 0.25) applied to accommodate loss of performance over time

d) Secondary flows shall be provided for the water which will follow during events that exceed the design capacity of the soakage device

e) Confirmation that the soakage system will not have an adverse effect on surrounding land and properties from land stability, seepage, or overland flow issues

http://www.hamilton.co.nz/our-services/building-consents-and-information/Documents/soak%20up%20your%20stormwater.pdf

http://www.hamilton.co.nz/our-services/building-consents-and-information/Documents/soak%20up%20your%20stormwater.pdf



f) Pre-treatment device to minimise silt ingress

g) Interception of hydrocarbons from nearby contaminated sites

h) Access for maintenance

i) A discharge permit may be required from the Waikato Regional Council

j) Soakage devices must not be located close to buildings

A clearance of 3.0m is generally required, but this can be reduced to 1.0m for porous paving. Where it is not practically possible to meet these guidelines, a site-specific geotechnical design (including PS1 certification) must be completed to take into account the effect of the soakage device on building foundations.

k) Soakage devices must not be located close to property boundaries

A clearance of 3 m to footings is generally required, but this can be reduced to 1m for porous paving and can be reduced to 1.5m where the neighbouring property is required to have a 1.5m setback to any new building. Setbacks to roadside boundaries can be 0.5m (to avoid fence footings). Where it is not practically possible to meet these guidelines, a site-specific geotechnical design (including PS1 certification) must be completed to take into account the effect of the soakage device on building foundations and determine the risk of flooding to neighbouring properties.

l) Soakage devices should not be located beside retaining walls

For walls less than 2.0m high, the clearance must not be less than a horizontal distance that is equal to the retaining wall height plus 1.5m, unless a site-specific design (including PS1 certification) is carried out. The site-specific design must take into account geotechnical considerations, and ensure stormwater from the soakage device will not enter the cut-off drain for the retaining wall.

For walls higher than 2.0m, a site specific design must always be carried out.

m) Soakage devices must not be located within 2.0m of public sanitary sewers or 1.0m of private sewers.

n) Soakage devices must not be positioned on unstable slopes

o) Soakage devices are to be positioned above the ‘winter’ high water table unless specifically approved to operate as predominately summer soakage systems.

The peak soil wetness period for Hamilton is usually July-September. The position of the high water table can be estimated when boreholes or test pits are constructed from observations of soil colouration and wetness. If no high water table can be discerned in the field then a suggested adjusting factor for investigations done at other times is shown in Table 4-20

p) Soakage devices shall not be shared between properties, unless a legally constituted 'Body Corporate' is established to take responsibility for maintenance and eventual replacement

Refer to the appendix of this section for design templates.



Table 4-20: Groundwater Seasonal Adjustments

Time of Testing Adjustment to site observation - assume groundwater raises

Dec-March 1.0m higher than found during inspection

April-May, November 0.65m higher than found during inspection

June, October 0.35m higher than found during inspection

In some cases, e.g. where a deep sand bed exists or in peat areas, soakage systems can be installed to recharge the ground under favourable conditions and overflow during periods of high ground water. Specific design in liaison with Council is required.

4.2.14.1 Recharging of Peat

Stormwater management on peat soils provides a special design challenge that needs to be addressed with care. It is important to achieve the correct balance of soakage for the site so that the post-development soil-moisture condition models as closely as possible the pre-development condition. If this is not achieved then the soil-moisture condition will be either too dry (in which case shrinkage will occur) or too wet (and the site should not have been developed). It is therefore essential that the right amount of recharge of the peat and adequate provision of overland flow paths for the remainder of the water is achieved.

Council defines peat soils as those with greater than 300mm of peat between 0.5m and 4.0m depth of the natural ground surface.

Defining the right amount of soakage is very site specific and the best means of facilitating the release of the stormwater into the peat/soil will need to be considered on a site by site basis. For small developments where an extensive assessment of the issues is difficult, an acceptable solution will be the provision of a single well liner to take the runoff from each 50m2 of roof area. This will then have high level provision for overflow discharge to the Council reticulation or an overland flow path as shown in Drawing D4.5.

4.2.15 Stormwater Treatment and Detention Devices Design There are a number of treatment and detention options available, the preferred solution will either be identified in an approved ICMP/CMP or through discussions with Council. Council will assess options based on the following considerations:

• The lifecycle maintenance cost for Council • Land limitations such as available area, stability or ownership • The suitability of locating a device in the locality • The engineering capacity and efficiency of the device • The optimisation of landuse and detention and treatment facilities in the growth area

Proposed engineering and landscape designs or works shall be approved or rejected at the sole discretion of Council.

Options include (but are not limited to):

• Wetlands • Dry detention basins • Rain gardens



• Swales and filters

The use of wet ponds is discouraged and will only be approved once all other methods have been exhausted.

Where these devices are located within the transportation corridor reference shall be made to the Transportation and Landscaping Section.

4.2.15.1 Wetlands and Dry Detention Basins

Council preference is for wetlands and dry detention basins for detention purposes, and wetlands for water quality purposes.

Specific matters to be considered in wetland and dry detention basin design include:

a) Catchment area shall be greater than 1ha

b) Size calculated to achieve water quality volume

c) Forebay to capture coarse sediments

d) Wetland depth not to exceed 0.9m except for forebay

e) Majority of permanently wet area to be approximately 200mm deep

f) Sufficient detention time for sediment retention

g) Side slope stability

h) Shallow ledges or batters for safety

i) Ease of access and maintenance including mowing and silt clean out

j) Shape and contour for amenity and habitat value

k) Effectiveness of inlet and outlet structures

l) Overflow design and scour protection

m) Fish passage where appropriate

n) Pest control (for example mosquitoes and blue-green algae)

o) Discharge temperature control - submerged outlets, shading and underground outlet pipes

p) Potential effect on downstream aquatic ecology and habitat

q) Maintenance requirements

lf Council is to be ultimately responsible for maintenance it shall be located on land owned by, or to be vested in Council or protected by an appropriate easement in favour of Council.

Design and Construction Minimum Requirements

Minimum wetland and dry detention basin design requirements are as follows:

a) Embankments must be permanently planted if the slope ratio is steeper than 1 (vertical) to 4 (horizontal)

b) Any embankment that the Council determines is either too inaccessible or unsafe for regular grass mowing shall be permanently planted

c) Any discharge risers must have a 1.0m wide concrete apron or band around the external portion. Between this apron and 2.0m from the riser, carex virgata and/or carex geminata shall be planted on the embankment with mulch matting, unless otherwise



specified by the Council. No other plant species, including grassing, may be installed within 2.0m of the outlet

d) Aesthetic design elements shall be in keeping with local character. Consider:

i. Integrating planting into the wider environment such as streetscape and/or park setting so that the planting is seamless (where this is desired)

ii. Extending the footpath into wetland area as a boardwalk

iii. Making the wetland shape and edges aesthetically appealing

e) Ensure that the planting, once established, promotes desirable views and focal points of interest, and does not visually block traffic intersections, property entrances, pedestrian and/or cycleway paths

f) It shall not compromise the safety of adjacent properties or the community

g) Wetlands and dry detention basins are to be landscaped so that they:

i. Comply with engineering requirements

ii. Minimise ongoing maintenance

iii. Improve stormwater water quality discharge

iv. Retain existing bush areas and tree stands where possible

v. Become a community asset and positive visual amenity

vi. Provide, where possible, forage and habitats for native flora and fauna

h) Safety of the site is paramount by incorporating CPTED (Crime Prevention Through Environmental Design) principles (refer to Landscape Section)

i) A safety bench shall be provided between the normally dry water level and the deep water where deep pools of greater than 0.9m are proposed. The safety bench shall be between 0.3m and 0.5m below normal water level and between 0.5m and 1.0m wide. Additional safety bench(s) are required each 5.0m where slopes greater than 1:3 lead to a deep water pond. Safety benches are not required where fencing is applied as per Section 4.2.15.4. Stabilise aquatic and safety benches with emergent wetland plants and wet seed mixes

j) Planting plans to be submitted to Council for approval

i. Plant species allocations are to be specific to soil type and conditions, site topography and exposure, post-development groundwater table levels and alignment with local indigenous native plant species. Plant species are to be indigenous to the Waikato Region, although native New Zealand grasses are permitted. Likewise, plants are to be eco-sourced where possible from the Waikato Region

ii. Of the vegetation mix in wetlands at least 10 percent and no more than 25 percent must be staked 1.5 m high grade trees

iii. Woody vegetation and trees are not to be planted within 3.0 m of the slope toe of wetlands and ponds to prevent future bank stability issues when the plant reaches the end of its lifecycle and its root systems decompose

iv. Vegetatively shade inflow and outflow channels as well as those areas of the wetland with a northern exposure to reduce thermal warming



k) Dry detention basin planting may be staged to minimise slope erosion. The initial stage shall be grassing the site with the Council approved grass mix, followed by landscape planting once grass has established

Maintenance Access

Access to wetland and dry detention basins shall be as follows:

a) A 4.0m wide access driveway and platform (as applicable) with all-weather surface suitable for an 8.2 tonne axle weight vehicle, at a grade of less than 1:12 shall be provided

b) The excavator working platform shall be level and adjacent to the clean out area

c) The excavator working platform shall be no higher than 2.0 m above the base of the clean out area

d) If the access path is greater than 50m long then a 3-point turning area for a 10 tonne rigid truck adjacent to device (in addition to the excavator working platform); shall be provided

4.2.15.2 Rain Gardens

Rain Gardens are engineered bioretention systems designed to use the natural ability of flora and fauna to reduce stormwater volumes, peak flows and contaminant loads. They can be designed for either infiltration to groundwater or discharge to the downstream network. Rain Gardens can be used in place of conventional landscape areas and contribute an attractive urban design feature as well as having an ecological value.

Minimum Requirements

It must be demonstrated that a Rain Garden complies with the following:

a) Capacity for a 10% AEP storm event without significant scour or erosion

b) Appropriate functionality and adequate capacity

c) Size is calculated to achieve water quality volume

d) Entry and overflow positions to restrict short circuiting

e) Appropriately planted (for wet and dry conditions) in accordance with Section 4.2.15.5 and incorporating a mulch, pebble or rock surface layer. Plants selected shall be a mix of groundcovers, shrubs and/or small trees (up to 4m high) that are able to withstand periods of soil waterlogging according to the Marginal and Lower Bank Planting Zone plant species

f) Where Rain Gardens occur in the transportation corridor, ensure species used from Table 4-22 align with transportation corridor planting requirements (refer to Landscape Section). Other species may be used with Council approval

g) Ensure that no large trees are selected that may impede maintenance requirements and/or require a resource consent for removal should this be required in the future. No mulch should be visible once plants have matured

h) A planting plan shall be submitted to Council for approval

i) Rain gardens are to be planted according to Section 4.2.15.5



4.2.15.3 Swales and Filters

Swales (grassed channel, dry swale or wet swale) covey stormwater via a open channel. They do not pond water for a long period of time and induce infiltration. Swales generally have a trapezoidal or parabolic shape with relatively flat side slopes.

Minimum Requirements

Vegetated swales will only be considered in limited circumstances within Hamilton due to conflicts with services, road design and ongoing maintenance requirements. Early consultation is encouraged with Council to determine the requirements.

Specific design matters to be addressed include:

a) Catchment area not greater than 4ha

b) Longitudinal slope 1% - 5%

c) Slopes flatter than 2% may require under drains if soakage is insufficient

d) Slopes greater than 5% may require check dams to reduce effective gradient to less than 5%

e) Capacity for a 10% AEP event

f) Velocity not greater than 1.5m/s in a 10% AEP event unless erosion protection is provided

g) Grass length 50mm - 100mm

h) Refer to Table 4-22 for species to be planted

i) Avoid planting woody vegetation adjacent to swales to prevent overshadowing

j) Vegetated Filters are to be planted according to Section 4.2.15.5.

k) A planting plan shall be submitted to Council for approval

l) Swale surface treatments shall be established with low maintenance treatments such as rolled turf (for short lengths), planted up in approved Carex species or laid with loose river rocks. Acceptance of swales and their surface treatments shall be at the Council’s discretion

4.2.15.4 Fencing of Stormwater Structures and Watercourses

Any part of stormwater structures having either a vertical drop of 0.9 m or the ability to fall directly into standing water of depth greater than 0.9 m shall be fenced in 50% permeable format and otherwise compliant with the Building Act.

Note: Fencing across overland flow paths is controlled by the relevant District Plan and requires approval by Council.

Council encourages early consultation between Developer and Council staff to achieve mutually beneficial design outcomes. Of particularly note Council seeks design outcomes that meet functional requirements whilst avoiding poor visual results.

4.2.15.5 Planting

In addition to the aesthetic appeal and ecological benefits, plants in and around detention and treatment devices contribute to the functional requirements such as trapping sediment and preventing scouring of the embankments.



The following planting zones define the planting regimes within detention and treatment devices. They are intended for wetlands but can be applied to other devices and are based on vegetative tolerances to wet/damp roots and frequent/infrequent inundation. Refer to Table 4-22 for approved plant species.

Due to site conditions and detention and treatment device configuration it may not be feasible for all Planting Zones to be used within a device. Consult with Council to confirm the applicable Planting Zones.

Table 4-21: Planting Zones

Zone Description

Wet Zone This area is where the pond ground surface is capable of being permanently submerged and where the plant roots may be permanently water logged

Marginal Zone This area is likely to be submerged or partially submerged in a 50% AEP return storm event

Lower Bank Zone This is the planting zone between the Marginal Zone and Upper Bank Zone where plants may be occasionally submerged (in storm events more severe than the 50% AEP return period storm). Plants are able to withstand inundation for short periods of time

Upper Bank Zone This planting zone is generally above the spillway level. Plants are able to sustain damp roots for periods but should not be fully inundated

Plant Sourcing and Grade

Plants are to be eco-sourced from the Waikato Region where possible, from reputable nursery stock with grades that minimize potential mortality rates. It is strictly prohibited to transplant vegetation from existing wetlands and other such environments.

Plant grades are to be of a suitable size to ensure vegetation establishes rapidly with minimum mortality rates and/or replacement requirements. Refer to Table 4-22 for the minimum plant grades. Trees are to be a minimum grade of 1.5m high.

Species Selection

Species are to be selected with regard to good conformation, healthy robust root systems and low maintenance shall comply with Council’s planting policies.

Planting species are to be selected according to the planting list indicated in Table 4-22 and corresponding site topography and ecology unless there are more suitable plants according to site conditions and/or local ecology. Other possible species may be referenced from the Hamilton City Council Gully Restoration Guidelines or the Waikato University Vegetation Types of Hamilton Ecological District. Where trees, shrubs and groundcovers are to be planted within a transportation corridor, reference shall be made to the Landscaping Section.

Species selection considerations include:

a) Compliance with the Transportation and Landscaping Section in regard to sight distances where the treatment and detention device is within or near the transportation corridor

b) Engineering requirements, including improving post-treatment stormwater water quality



c) Ensuring that intended plants are not classified as regionally noxious weed or pest species

d) Longevity and corresponding maintenance requirements

e) Minimal leaf fall in autumn (which can reduce efficiency)

f) Pest and disease resistance

g) Shading consistent with location and adjacent landowners

h) Suitability to environmental conditions, for example, modified groundwater table, exposure to wind and frost, vehicular and cycle traffic

i) Ensuring no species that drop branches, debris, or may in any other way cause damming and/or unplanned flooding in and adjacent to watercourses (such as streams and spillways) are planted within 5.0m of watercourses.



Figure 4-6: Stormwater Wetland Staged Landscape Planting

Stage 1: Planting

Stage 2: Planting

Expected Result after 5 years



Table 4-22: Approved Plant Species

Botanical Name Common Name Minimum Centres

(m) **

Minimum PB Grade

Type

APP

LIC

AB

LE P

SDPO

ND

& W

ETLA

ND

Upp

er B

ank

Zone

Low

er B

ank

Zone

Mar

gina

l Zon

eW

et Z

one

(Dep

th ra

nge

in b

old)

RA

IN G

AR

DEN

VEG

ETA

TED

SW

ALE

VEG

ETA

TED

FIL

TER

TOLE

RA

NC

EPe

at S

oil

Fros

tW

et /

Moi

stD

ryW

ind

LIG

HT

REQ

UIR

EMEN

TSFu

ll Su

nPa

rt S

hade

***

Full

Shad

e **

*C

HA

RA

CTE

RIS

TIC

SR

apid

Gro

wth

Nur

se P

lant

Bird

For

age

Apodasmia similis Oioi / Jointed Rush 1.00 RT Medium RushAristotelia serrata Wineberry 2.00 5 Small Tree XArthropodium cirratum 1.00 3 Low ShrubAsplenium bulbiferum Hen & chicken fern 1.0 5 Low FernAstelia grandis 1.00 3 Medium ShrubBaumea articulata 1.00 RT High Rush 0.30mBaumea rubiginosa 1.00 RT Low RushBlechnum novae-zelandiae Kiokio 1.00 3 Medium FernCarex dispacea 1.00 RT Sedge >Carex dissita 1.00 RT SedgeCarex gaudichaudiana 1.00 RT SedgeCarex geminata 1.00 RT Sedge > 0.05mCarex secta 1.00 RT Sedge > 0.05m ?Carex testacea 0.30 RT SedgeCarex virgata 1.00 RT Sedge >Coprosma grandifolia Raurekau 1.00 5 Tall Shrub XCoprosma 'Hawera'* 0.50 3 Groundcover XCoprosma kirkii 'Minogue' 1.00 3 Groundcover XCoprosma propinqua Mingimingi 1.00 5 Tall Shrub X Coprosma rhamnoides 1.00 5 Tall Shrub XCoprosma rigida 1.00 5 Tall Shrub XCoprosma robusta Karamu 1.00 3 Tall Shrub XCoprosma tenuicaulis Swamp Coprosma 1.00 5 Tall Shrub XCordyline australis Cabbage tree 1.00 3 Small Tree X 0.10mCortaderia fulfida Small Toe toe 1.00 RT Small GrassCortaderia toe toe Toe toe 1.00 3 Medium GrassCyathea dealbata Ponga 1.00 8 Tree Fern XDacrycarpus dacrydioides Kahikatea 2.50 1.5m High Tall Tree XDianella nigra 1.00 5 Small Shrub XDicksonia fibrosa Wheki ponga 1.00 8 Tree Fern XDicksonia squarrosa Wheki 1.00 8 Tree Fern XDodonea viscosa Ake ake 2.00 5 Small Tree XEleocharis acuta Sharp spike rush 1.00 RT Low Rush 0.20mEleocharis sphacelata Kuta 1.00 RT Low Sedge 0.40mFuschia excorticata Kotukutuku 2.50 1.5m High Medium Tree XGriselinia littoralis Papauma 2.50 1.5m High Medium Tree XHebe paviflora* 1.00 3 Medium ShrubHebe stricta Koromiko 1.00 3 Medium ShrubHebe 'Wiri Cloud'* Hebe cultivar 0.50 3 Small ShrubHebe 'Wiri Splash'* Hebe cultivar 0.50 3 Small ShrubHoheria sextylosa Lacebark 2.00 5 Small Tree XKunzea ericoides Kanuka 2.50 3 Tall Tree XLeptospermum 'Crimson Glory'* Manuka cultivar 1.00 3 Small ShrubLeptospermum scoparium Manuka 2.00 3 Small Tree XLibertia ixioides NZ Iris 0.50 3 Small ShrubMelicytus ramiflorus Mahoe 2.00 3 Medium Tree XMyrsine australis Mapou 2.00 3 Medium Tree XPhormium cookianum Wharariki 1.00 3 Medium Flax XPhormium 'Green Dwarf'* Flax culitvar 1.00 3 Low FlaxPhormium tenax Harakeke 1.00 3 Medium Flax X 0.15mPittosporum crassifolium* Karo 2.00 3 Small Tree XPittosporum eugenoides Lemonwood 2.00 3 Small Tree XPittosporum tenuifolium* Kohuhu 2.00 3 Small Tree X No NoPittosporum tenuifolium 'Mountain Green'*

Kohuhu cultivar 2.00 3 Small Tree X No No

Plagianthus regius Ribbonwood 2.50 1.5m High Medium Tree XPodocarpus totara Totara 2.50 1.5m High Tall Tree XPseudopanax ferox Fierce Lancewood 2.00 5 Small Tree XSchefflera digitata Pate 2.00 5 Small Tree XSophora 'Dragons Gold'* Kowhai cultivar 2.00 5 Small ShrubSophora microphylla Kowhai 2.00 1.5m High Small Tree X Streblus heterophyllus Turepo 2.00 3 Small Tree X NoSyzgium maire Swamp Maire 2.50 1.5m High Tall Tree XTyphus orientalis Raupo 1.00 RT RushGrassing GroundcoverRoll-on Turfing GroundcoverKEY: These species may be planted according to PSD requirements and species tolerances. Only those nominated cultivars are acceptable unless approved otherwise by Council.

> Indicates that the vegetation mix for this planting zone should have a high percentage of this plant.

** Minimum staggered centres unless otherwise specified. Tree centres indicated are the minimum distances from other tree species and are to be underplanted with 4 equidistant same species groundcovers at 0.75m centres from tree trunk/stem. *** Light Requirements: Those species that cannot tolerate Full Sun are not to be planted until after the initial planting stage has formed sufficient canopy to provide understorey

* Plant species is not indigenous to the Waikato region, but is an approved PSD plant. # Swales: Plant only on slopes. Forms trunks that impede water flow.

X Plant must not be planted in the Marginal Zone as they may damage the slope toe should they fall over and/or require future removal.



Swales and Filters Planting

Swales may be turfed or grassed to ensure rapid establishment and mitigate channel surface scouring. Generally, grass needs to be maintained at heights between 50mm and 150mm, depending on engineering design parameters.

Where engineering requirements permit, Carex virata or Carex geminata may be planted in the Wet and Marginal Zones. No other groundcover, shrub or tree species are permitted in these Zones. These need to be planted with mulch rounds.

Table 4-23: Swale Planting - Velocity/Grade Matrix

Type Grade Velocity

Swale – Roll on Turfing Less than 2% Less than 1.5m/s at 10 year ARI flow

Swale – Vegetated (Carex grasses)

2-5% Less than 2.5m/s at 10 Year ARI flow

Swale – Rocks Greater than 5% 2.5m/s or greater at 10 Year ARI flow

Turfed swales shall be prepared, established and maintained as per the Landscaping Section. Both during and post-establishment, the height of the turf shall be consistently maintained at least fortnightly to designed stormwater engineering requirements. Turf shall be of a drought-resistant hard-wearing rye-grass based variety with no weeds species.

Swales planted with Carex species shall be planted according to the Landscaping Section.

Filters can be planted with a mix of Council approved groundcovers, shrubs and tress from Table 4-22 according to the Planting Zone criteria, as site conditions and engineering requirements permit.

4.3 Construction and Maintenance

4.3.1 Pipeline Construction All pipeline’s, bedding, trenchless construction, jointing, manholes and reinstatement shall be in accordance with the wastewater section.

4.3.2 Catchpits The connection of the lead into the catchpit shall be constructed as detailed in Drawings D4.6 – D4.10.

4.3.3 Connections All connections shall be sealed by removable caps until such time as they are required.

All connections and disconnections to or from Council pipes and all works outside the property boundary shall be undertaken by Council.

Connections shall be constructed as per drawing D4.4



4.3.4 Outlets The Developer shall be responsible for the structural integrity and maintenance of the bank stabilisation/erosion protection structures and for any erosion control works that become necessary to preserve the integrity and stability of the stream, river, channel or water course and/or to control erosion until the structure is vested.

4.3.5 Stormwater Treatment and Detention Devices 4.3.5.1 Stormwater Wetland and Dry Detention Basin Planting

Stormwater wetlands and dry detention basins are to be planted up as soon as possible after civil construction is completed according to the Planting Zones indicated in Section 4.2.15.5. All stormwater features with an inner batter slope ratio of 1 (vertical) to 4 (horizontal) or steeper must be landscaped as the slope is too great for safe maintenance.

Where site conditions such as unstable soil structures require a more rapid groundcover than shrubs and trees provide, exposed surfaces above the Upper Bank and Lower Bank Planting Zones shall be stabilised with grassing prior to landscape planting.

Planting within the Marginal Zone shall be installed at the same time that the upper slopes receive grassing to minimise slope toe erosion. The Wet Zone shall be planted up once the normal standing water level has been achieved. Refer to Figure 4-1: Hamilton City Flood Hazard Classification Matrix.

Pond plant species shall be a mix of Council approved groundcovers, shrubs and trees from Table 4-22 as site conditions and engineering requirements permit.

Where feasible, consider placing rough logs, dead trees (snags), large rocks/boulders in select locations to encourage wildlife habitats. Ensure that the slope stability, slope toe, inlet, outlet, water flow and forebay are not compromised by the placement of these items and that maintenance can be carried out. Ensure no soil compaction occurs during the installation in surrounding area. The Developer shall consult with an Ecologist and Council prior to material selection and placement.

Minimum planting provision requirements are:

a) Quick establishment of plant cover is required throughout the site, as engineering requirements permit

b) No material storage or heavy equipment is to be stored within the site or buffer area after site clearing except to excavate and/or grade site

c) All construction and other debris are to be removed prior to topsoil placement

d) Soil testing and making adjustments is required (refer to Landscape Section)

e) Unless existing soil is unstable, sloped soils shall be ripped 150mm deep either in a criss-cross pattern or horizontal to base (following contours) prior to topsoil application. Heavy clay will need deeper ripping. Topsoil shall be spread to a minimum 200mm depth, ensuring heavy equipment does not compact the slopes

f) Where bark mulch is used, it is to be contained within the plant area that it is providing cover for. Other mulch applications are to be utilised on slopes greater than 1:3



4.3.5.2 Staged Wetland Planting

The staged planting shall be as follows.

Stage 1: Grassing

Banks shall be prepared and sown with grass seed to establish rapid ground stabilisation, according to the Landscaping Section.

Where plants are to be established in nitrogen-deficient soils and at Council’s discretion, the seed mixture shall be:

• Annual Rye Grass 150 kg/ha • Sweet Clover 100 kg/ha

All seed shall be certified and less than 12 months old at the time of sowing. The Ryegrass component is to be certified as having greater than 80% live endophyte content. Council may prohibit the use of seed that has deteriorated because of wetting, fertiliser burning, etc. Otherwise the standard landscaping grass seed specifications shall apply as per the Landscaping Section.

The site shall be grassed for at least three months and meet establishment requirements for sown areas prior to landscaping. Marginal Zone planting and mulching shall be established at Stage 1.

Stage 2: Landscape Planting

Stage 2 planting shall occur within the Council planting season (2 April to 30 September) once Stage 1 sown grass has established. Ensure that no weed species exist throughout the site. Where weed species need to be eradicated either carefully spot spray and/or hand-pull in such a manner that erosion is minimised and surrounding groundcover remains undamaged. The sown grass groundcover shall be spot sprayed to 0.50m diameter for each location where individual plants are to be planted four weeks prior to planting, ensuring that the established grass between spot sprays remains undamaged. Maintain sprayed areas so that no new weed growth exists at time of planting. Install and establish planting and mulching as per the Landscaping Section.

4.3.5.3 Plant Spacing

Plants are to be planted according to the following spacing allocations.

a) Trees, shrubs and groundcovers, as per Table 4-22 required spacings

b) Within the Marginal Zone, Carex shall be evenly staggered at 1.0m intervals

c) Where plantings are to include approved partially submerged species, these are to be irregularly clumped in groups of 3 to 7 plants along the circumference of the stormwater wetland/pond

d) For permanent stormwater ponds, plant 0.4m below the designed normal standing waterline, approved sedges and rushes

e) Amenity plantings of tussocks are to be clumped in groups of 3 to 10 plants

f) Trees shall be spaced at minimum 2.5m centres from other trees and underplanted with 4 equidistant same-species groundcovers, installed 0.75m from the tree stem. The groundcover species shall provide a weed suppression canopy while the tree is establishing, and as such will have no more than 1.0m mature height and minimum 0.75m spread. Ensure that the groundcover species does not compete with the tree establishment requirements. Depending on the Zone planting location, possible plants



could be Phormium 'Green Dwarf', various Carex such as Carex virgata, and Coprosma groundcovers such as Coprosma kirkii 'Minogue'

g) In respect to the maintenance access track

i. No shrub or groundcover centres are to be located within 1.0m of the track

ii. No trees centres are to be located within 2.5m of the track

iii. Plantings within 2.0m either side of the access track are to have species that are able to recover quickly should they become damaged during pond maintenance

iv. In subdivision and shopping precincts, planting design either side of the access track should also ensure that the track may be used for pedestrian amenity purposes

4.3.5.4 Staking and Protection

Trees 1.5m High or Greater

Newly planted trees shall be staked with 2no. 50mm x 50mm x 1.8m rough sawn Pine H5 treated stakes with at least one third of their length (600mm) in the ground and at least 1.0m exposed minimum, or as specified on the plan with the approval of Council. All stakes shall be inserted to avoid hitting the root ball. Stakes shall be at least 400mm away from the tree trunk and no more than 500mm away.

Two flexible ties per stake shall be attached. Ties shall be tensioned to avoid chafing of the tree against the stakes but with enough play for the tree to move in the wind. All ties shall be fixed to the stakes. Ties shall be of a type approved by Council prior to tying. Ties are to be fixed to the outer stake face with a minimum of four staples in a square pattern.

Smaller Grade Staking

• All tree species planted at Pb3 to Pb18 grades • All shrub species planted at greater than Pb8 grades

Shall be staked with a single 1.2m minimum long 22mm - 25mm diameter dead bamboo stake, positioned outside the rootball, driven into the ground to at least a 400mm depth. The stake is to be fastened two thirds up the plant stem/trunk with a Council approved interlocking tree tie (e.g. Treelock). If the tree tie is not biodegradable:

• The tie shall be adjusted periodically so that the stem/trunk does not become damaged or the stem/trunk grows over the tie.

• The tie shall be removed at a time designated during the design phase of the landscape planting.

Some nursery-supplied plants are provided with a stake attached, usually directly against the main stem. This stake is to be removed and replaced according to this specification.

4.3.5.5 Plant Status

Refer Landscape Section for plant status and planting definitions Table 7-5.

4.3.5.6 Site Preparation

In regard to adjacent water bodies and/or courses, ensure that no debris or chemical spray enters or impedes the functionality of the water body, whether it is natural or manmade.



4.3.5.7 Mulching

All areas shall be mulched except for areas that are grassed or turfed. All mulch is to be approved by the Council prior to spreading.

The types of mulching specified are to ensure rapid planting establishment while maintaining good ground infiltration without souring the soil or causing negative amenity values, and allowing some scope for landscape design variations. Mulching shall be as detailed in Table 4-24.

Council favours biodegradable weedmats over synthetic geotextile weedmatting. No synthetic geotextile weedmatting or weedmatting with synthetic geonet content is to be utilised in the installation of the landscaping portion of landscaping engineered stormwater devices. However, synthetic geotextiles and other materials may be used, as applicable, to meet device engineering requirements; for example, at inlets, outlets and high velocity channels. Biodegradable matting must:

• Be a single layer of biodegradable mulching fabric or material without synthetic geonet or geotextile content with at least 1000 g/m2 density composed of approximately 4 to 5 inch long coir fibres, and preferably a 100% rubber-based binder

• Have a minimum of 24 months life expectancy and be fully biodegradable into soil within six years

• Prevent weed growth within the mulched area • Help stabilise the soil while plants are establishing • Not easily lift from the ground if submerged for periods of time • Appear tidy from a visual amenity perspective

A simple test to ascertain whether the mulching fabric is viable is to hold a sample to the sky. It should be mostly opaque. This density inhibits weed seeds trapped under the mulching fabric from sprouting, provides good moisture retention and assists with batter erosion control.

At Council’s discretion, mat rounds may be used instead of matting. These shall be a minimum 500mm diameter and have the same characteristics as the mulch fabric. Each round shall be secured to the ground with eight pins: four pins equidistant near the outer edge and four pins around the plant stem. Pins shall be a minimum 300mm long to prevent Pukeko removal.

Landscape Section technical specifications apply where bark mulch is used. Ensure it is contained within the plant area that it is providing cover for. Likewise bark mulch is not permitted:

• Within 3.0m of any watercourse or water body • Where water ponding or flooding may occur • On slope gradients of greater than a 1:3 ratio

Biodegradable coir netting and staked coir logs may be used in high erosion sites as the Landscaping Section.

4.3.5.8 Amenity Areas Mulching

Landscape planting between the drainage reserve boundaries to the Upper Bank Zone shall only be mulched with bark or aged woodchip mulch where there is no possibility of surface ponding, flooding or mulch travel. Where surface ponding, flooding and mulch travel is possible within this area, biodegradable weed matting shall be used for all landscape planting.



4.3.5.9 Upper Bank and Lower Bank Zone Mulching

All plants shall be mulched with Council approved 0.5m diameter biodegradable weed mat rounds that shall be secured around plants, allowing adequate room around the stem for future growth. Firmly secure fabric mulch with wooden or other biodegradable pegs as per the manufacturer’s instructions so that the fabric mulch does not detach from the soil, during inundation and high winds.

4.3.5.10 Marginal Zone Mulching

Council approved biodegradable weed mat is to be laid in a manner that the mulch will not uplift during inundation. Ensure that plants have adequate room around the stems for future growth.

4.3.5.11 Wet Zone Mulching

No mulching is required within the Wet Zone.

Table 4-24: Approved Mulching

Device Planting Zone Mulch Type

Rain garden All Council approved biodegradable weed matting

River rocks (with a diameter of between 50mm and 150mm) in gabion mats (100mm to 300mm deep) may be permissible depending on stormwater engineering requirements and long term maintenance requirements.

Stormwater Wetland Amenity Planting – Site Entrance and Drainage Reserve Boundary Line to Upper Bank Zone where no ponding, flooding or mulch travel is possible

Council-approved bark and/or aged woodchip

Amenity Planting – Site Entrance and Drainage Reserve Boundary Line to Upper Bank Zone where ponding or flooding is possible

Council-approved biodegradable weed matting

Upper Bank and Lower Bank Zones

Council-approved 0.5m diameter biodegradable weed matting rounds

Marginal Zone Council-approved biodegradable weed matting

Wet Zone No mulch required

Swale – River Rocks All Loose 50mm - 150mm diameter river rocks



Device Planting Zone Mulch Type

on biodegradable weed mat

River rocks of 50mm - 150mm diameter encased in gabion matting

Swale – Roll-on Turfing All No mulch

Swale – Vegetated (Carex grasses)

All Council approved biodegradable weed mat or secure biodegradable mat rounds

Grass Filters Strips All No mulch

4.4 Defects Liability

4.4.1 Defects Liability Periods The following Defects Liability Periods apply to all planted treatment and detention devices, after obtaining Council’s approval as per Section 4.4.

Table 4-25: Defects and Liability Periods

Type Defects Liability Period

Dry detention basins – Permanent Grass without Planting

Where Stormwater dry detention basins are to be permanently grassed, the Defects Liability Period for the grassing is a minimum of six months if sown between April 2 and September 30. If sown between October 1 and April 1 the period is extended for a further six months.

Dry detention basins – Staged Planting

Stage 1: Temporary Grassing

The Stage 1 Grassing Defects Liability Period will extend for a minimum of six months or until such time as Stage 2 Planting is investigated

Stage 2: Landscape Planting

The Stormwater Pond Stage 2 Defects Liability Period shall be a minimum of 12 months except when planting is carried out between October 1 and April 1 the Defects Liability Period shall be extended for an additional six months.

Wetlands As per dry detention basins

Rain Gardens, Swales and Filters

Raingardens, Swales and Filters shall have a minimum 12 month Defects Liability Period, except when planting is carried out between October 1 and April 1 the Defects Liability shall be extended for an additional six months



4.4.2 Defects Maintenance Requirements The Developer shall be responsible for the routine maintenance of the landscape planting works including weeding, mulching, replacement of plants and watering during the defects liability period.

The minimum standards required during the Defects Liability Period shall be as per Table 4-26.

The Developer at the end of the required defects liability period shall advise the Council at least 7 working days prior to the proposed commencement of Council approved acceptance of the asset and its on-going maintenance.

Table 4-26: Defects Period Maintenance Schedule

Maintenance Type Sub-Type Regime Frequency (months)

Mulching bark Check and ensure that mulch has not deteriorated nor travelled below the Upper Bank Zone

12

Replace where quality and depth has diminished below specification requirements. Bark should only be topped up during winter or spring

Biodegradable matting

Check, repair or replace any matting that has rips and non-plant stem holes. Matting should remain intact for minimum 24 months post-planting installation

6

Biodegradable rounds

Check and ensure rounds are intact and remain properly pegged around plant stems for minimum 24 months post-planting installation. Remove any weeds that have uplifted rounds

3

Permanent grass Check and ensure that permanent grass is establishing and maintained to a minimum 100mm height and maximum 200mm height in accordance with the Landscaping Section

3

Planting establishment

Check and ensure all installed plants are healthy and free of pests, disease, spray and weed-trimmer damage, and are growing generally consistent with the species type shape and form

3

Where plants are not establishing, either remediate or replace plants

Installed trees Check and ensure that trees remain staked as per specifications

3

Check and ensure that all trees are growing upright




Self-seeded trees Remove all self-seeded trees from the Wet Zone and Marginal Zone without damaging embankment toe and installed plants. Use systemic pre-mix picloram gel where this is not feasible

3

Replacements Keep a record of all replacement plants installed, including the plant species botanical name, plant grade, quantity and date(s) planted

As required

Replacement installations should only occur between 1 April to 1 October each year in the Marginal, Lower Bank and Upper Bank Zones. Planting in the Wet Zone may occur in any season as long as the soil is moist to a depth of 300mm at the location of planting

Rubbish Check and remove any domestic rubbish or building material within the site

3

Soil moisture Check and ensure that all areas with installed planting have soil that is moist to a 200mm depth. Irrigation may be required during summer if planting installation was late spring-early summer

3

Stormwater inlets and outlets plant cover

Ensure that no plants are evident within 1.0m of the stormwater inlet and outlet pipes

3

Swale maintenance channel

Check and remove weeds, dead plants, debris dams and pest damage

6

Remediate any channel surface scouring that has occurred

Ensure that Wet Zone plants are no higher than 0.5m high

Remove any non-installed plants from the swale channel

Vegetative waste Ensure that all vegetative waste is safely removed and disposed of offsite

3

Check and remove any vegetative debris that is blocking the access track

Weeds noxious plants

Check, remove and dispose of safely all noxious plants, including root systems

3

Notifiable plants Notify Waikato Regional Council should any 3




notifiable weeds be identified

Weed cover Check and ensure that there is no more than one 300mm high weed per 1.0m2

Weed control Check and ensure that all plants are fully weed-released

3

Weeds may be controlled by weed-trimming, chemical or steam spraying, hand or other manual releasing unless otherwise specified

Chemical spraying Ensure that no chemical spraying occurs in the Wet Zone and Marginal Zone. All weeds growing in these Zones must be removed by other means

As required

4.4.2.1 Spraying and Weed Control

Chemical weed control shall be carried out in accordance with the Landscape Section ensuring that no spray enters any water body or watercourse.

In respect to wetland, where weed species exist both on and within 2.5m adjacent to the normal standard waterline, weeds shall be controlled by either hand-pulling or weed-eating in such a manner that no debris enters any water body or watercourse.

Unwanted woody vegetation, such as Salix caprea (Pussy Willow), must not to be removed with hand-pulling or weed-eating. Use a systemic pre-mixed gel containing picloram according to manufacturer’s instructions.

4.4.3 Final Defects Inspection Criteria To achieve final Defects Liability approval, the stormwater treatment and detention device shall meet the following ‘planting’ criteria as outlined in the following tables where applicable.

Percentages indicated are based on the total quantity of plants specified on the approved Planting Plan Plant Schedule.

Note: Any defects liability period extensions shall apply to the whole of the site.

Table 4-27: Planting Establishment

Zone Planting Establishment Requirements

Wet Zone 75% planting established

25% establishing.

Marginal Zone 100% plants established

Lower Bank Zone

Groundcovers:

• 75% established

• 25% establishing



Shrubs:

• 50% established


All trees establishing

Upper Bank Zone

Groundcovers:

• 75% established


Shrubs:

• 50% established


All trees establishing

Plant Canopy Lower and Upper Bank Zone groundcover canopy is providing 50% minimum cover over ground surface

Planting Density Installed plantings are at the approved consent planting plan centres

Table 4-28: Minimum Inspection Requirements

Inspection Minimum Requirements

Loose Mulch (for example, bark)

• 75 mm minimum depth between plants and 25 mm maximum depth around plant stems

• No loose mulch is below the bottom edge of the Upper Bank Zone

Permanent Grass • Permanent grass has established and is maintained in accordance with the Landscape Section

Planted Areas Soil • All planted areas shall be moist to at least 200mm

Replacements

• All replacement plants that have been installed due to plant failure have been successfully establishing on site for at least three months. Council may request replacement records to verify installation dates

• No more than 25% replacements have been installed three months prior to the final defects inspection

• More than 25% replacements shall incur a 12 month minimum defects extension

• Should the final defects inspection find that areas of the device require replacement planting:

o Less than 25% replacements shall incur an additional three months defects period after replacement planting has been completed to Council’s approval, if the replacement planting occurs between 1 April and 1 October, otherwise the extended defects shall be six



months minimum.

o More than 25% replacements shall incur an additional 12 months defects period after replacement planting has been completed to Council’s approval.

Rubbish

• No rubbish, including domestic and building material is evident within the Drainage Reserve, or where the device is located elsewhere, within 5.0m of the device

Spraying • There is no evidence of installed plants killed or severely damaged by weed spraying.

Stormwater Inlets and Outlets

• No plants are evident within 1.0m of the inlet and outlet pipes.

Trees

• Where trees were installed with stakes, the trees are staked and tied as per this specification.

• Trees are upright, healthy, free of disease and pests, without spray or weed-trimmer damage, and of good conformation

• No self-seeded trees are growing within the Wet or Margin Zones

Weed Cover

• The device has no noxious or Waikato Regional Council notifiable plants evident

• There is no more than one 300mm maximum height weed per 1 m2 within the device

• All plants are fully weed released

• There is no evidence of vegetative waste within the Drainage Reserve, or where the device is located elsewhere, within 10m of the device.

Weed Matting

• Within 24 months of planting installation, biodegradable matting remains intact, has no non-plant stem holes or rips, and has not become brittle enough for a hole to be created if stood on by an adult wearing safety boots

• Where matting rounds have been used:

o These are intact

o Are properly pegged to the ground around plants as per manufacturer’s instructions; and

o Have no weeds uplifting them from underneath the round.

4.5 Approval of Proposed Works

4.5.1 Piped network Refer to Wastewater Section.



4.5.2 Stormwater Treatment and Detention Devices Approval process for stormwater treatment and detention devices is as follows.

Table 4-29: Stormwater Devices Transfer Process

Stormwater Facilities Transfer (Flow Chart for Developer)

PLAN

Consent issued requiring stormwater detention and treatment facility. Submit engineering plans for approval including a planting plan and proposed operations and maintenance plan

Apply for WRC resource consents and building consents if stormwater activity is not permitted and retaining structure required

CON

STRU

CT

Construct facility once plans are approved and necessary consents obtained. Comply with HCC and WRC consent conditions

Carry out mulching and landscaping to the approved planting plan

MAI

NTA

IN

Apply for first ‘defects liability’ inspection (notify Council seven days in advance). Complete checklist. Once all works satisfactory, Council will notify Developer to initiate defects liability period

During defects liability period carry out maintenance requirements of facility and rectify problems as they occur (e.g. weed and plant mortality). Comply with consents. Council will undertake audits during this time

At the end of the defects liability period, apply for a final ‘defects liability’ inspection. Council must be notified seven days in advance. Carry out further works as required

TRAN

SFER

Apply for 224c approval once: • All weather access is provided to the forebay • Physical works completed to in accordance with the approved plan • As-built plans and datasheets have been submitted • Planting has been completed in accordance with the approved plan • Operations and maintenance plan has been received and approved • Site complies with Checklist, including approval of defects liability inspections

Vested to Council via 224C approval

Request WRC transfer Discharge Consent to Council ownership

NOTE: To obtain 224c the device has ideally been completed to standard and the defects liability period is complete. If the defects liability has not yet lapsed, consult with Council about options for obtaining 224c. This will include requirements such as a programme of works detailing who will undertake the maintenance during the defects liability period and the proposed process for



transferring ownership of the device to Council at a later date.


Last Updated: 3 December 2012

Appendix A Forms and Checklists

Table 4-30: Forms and Checklists

No. Title

F4.1 Stormwater Calculation Summary

F4.2 Falling Head Percolation Test

F4.3 Falling Head Percolation Graph

F4.4 Stormwater Detention Calculation

F4.5 Nominal Soakage Design

F4.6 Detention Tank Design

F4.7 Detention Tank Design

F4.8 Wetland and Dry Detention Basin Management Manual Checklist

F4.9 Wetland and Dry Detention Basin Inspection / Signoff Checklist

F4.10 Quality Assurance Design Certificate

F4.11 Pipe Laying Checklist

F4.12 Manhole Checklist

F4.13 Trench Backfill Compaction

F4.14 Catchpit Checklist

F4.15 Final Inspection

Design Templates Stormwater Calculation Summary

F4.1 Infrastructure Technical Specifications

Version: October 2012 Page 1 of 1

Site Address:

Consent Number:

Application by:

Residential Infill Residential to road

Total Site Area Prior to Subdivision 2000

Lot 1 Area 2000

Lot 2 Area 0

Lot 1 C

0.37

Lot 2 C

1 Design Storm Details 2 ARI

Soakage Viable Yes

Lot 1

Provide 49 number 900 mm soakholes

or 21 metres of 1.0 m*1.5 m*1.5 m rock filled soak trench

or 14 metres of 1.0 m*1.5 m*1.2 m aquacell trench

126 aquacell units

Lot 2

Provide 0 number 900 mm soakholes

or 0 metres of 1.0 m*1.5 m*1.5 m rock filled soak trench

or 0 metres of 1.0 m*1.5 m*1.2 m aquacell trench

0 aquacell units

Detention

Allowable runoff flow rate into HCC reticulation 31 litres/second

Lot 1 Share 100 %

Lot 2 Share 0 %

31 l/s

0 l/s

Lot 1 provide

Lot 1 provide minimum 0 litres detention

minimum 0 litres detention

orifice 0 mm diameter

orifice 0 mm diameter

Design Templates

Worksheet 1 Falling Head Percolation Test



Site Address:

Completed by: Date:

Qualification: Chartered Engineer Civil Engineer Engineering Technician Engineering Geologist Drain Layer Other _________________ Registration number ___________________ (tick one)

Date of test: Season:

The following procedure has been carried out

Hole kept full for 17 hrs. prior to test Hole kept full for 4 hrs. prior to test

Drop in water level recorded at intervals of 30 mins (or less)

Test continued for 4 hrs. Test continued until bore empty

Test stopped at 0.25 m above base Hole refilled at 0.25 m above base

(tick when complete) Signature:

Test Details

Bore hole reference ref:

Diameter of bore D= ____.____ mm

Depth of bore ____.____ mm

Time (min) Depth (mm) Time (min) Depth (mm)

Calculations

Soakage Rate Sr = Minimum Gradient * = 𝑌

𝑋

*a straight line interpolation between last points on graph 𝑦/𝑥 = = ____________mm/hr

Divide by 1000 for m/hr ____________m/hr

Design Templates

Worksheet 2 Falling Head Percolation Graph



Site Address:

Completed by: Date:

Bore ref:

1 2 3 4 0

2000

3000

1000

Wat

er D

epth

(mm

)

Time (hr)

Design Templates

Worksheet 3 Stormwater Detention Calculation

Summary – 2 Lot Development



Site Address:

Completed by: Date:

Pre-Development Site Runoff

Zone Residential Industrial Commercial

5 min storm intensity 2 year 5 year 10 year

Pre-climate Change I= _____ mm/hr _____ mm/hr _____ mm/hr

Total Site Area A= ________m2

Allowable Runoff From Site 𝑄 = 𝐶𝐼𝐴3600000

m3/s

Qallow= ____𝑋____𝑋____3,600,000

=

_______________m3/s

Note: litres/second = [(m3/s)*1000] [_______________l/s]

Developed site Lot 1


1 hr storm intensity _____ year _______ year _______ year

Post-climate Change I= _____ mm/hr _____ mm/hr _____ mm/hr

Lot 1 Area Alot1= ______________ m2

Equivalent Impervious Area

Cover Type Area (m2) Coefficient C Area x C

Roof Ar = 0.95

Paved Apv = 0.95

Pervious (lawn etc.) Ape = 0.3

Ae = ∑(𝐴𝑟𝑒𝑎 𝑥 𝐶)

Equivalent Runoff Coefficient Ceqv = 𝐴𝑒𝐴𝑙𝑜𝑡1

=

Runoff From Site𝑄 = 𝐶𝑒𝑞𝑣𝐼𝐴𝑙𝑜𝑡13600000

m3/s

Qlot1= ____𝑋____𝑋____3,600,000

=

_______________m3/s


Design Templates

Worksheet 3 Stormwater Detention Calculation

Summary – 2 Lot Development



Developed site Lot 2 Run-off


____ min storm intensity _____ year _______ year _______ year

Value from manual I= _____ mm/hr _____ mm/hr _____ mm/hr

Lot 2 Area Alot2= ______________ m2

Equivalent Impervious Area

Cover Type Area (m2) Coefficient C Area x C

Roof Ar = 0.95

Paved Apv = 0.95

Pervious (lawn etc.) Ape = 0.3

Ae = ∑(𝐴𝑟𝑒𝑎 𝑥 𝐶)

Equivalent Runoff Coefficient Ceqv = 𝐴𝑒𝐴𝑙𝑜𝑡2

=

Runoff From Site𝑄 = 𝐶𝑒𝑞𝑣𝐼𝐴𝑙𝑜𝑡23600000

m3/s

Qlot2= ____𝑋____𝑋____3,600,000

=

_______________m3/s


Design Templates

Worksheet 4 Nominal Soakage Design



Site Address:

Completed by: Date:

Area of additional impervious surface _____ m2

Note this needs to be <= 20 m2

Describe the general soil type [excavate a 1.0 m square hole, 1.0 m deep in the general area of the proposed soak pit]

Fill the hole with water

Does the water soak away within 24 hours? Yes – Use nominal soak pit as detailed on drawing _____ No – alternative method of disposal possibly required – refer to designer.

Design Templates

Worksheet 5 Soakage Design



Site Address:

Completed by: Date:

Area for lot number ___ from worksheet 5 Alot__ _____ m2

Equivalent Runoff Coefficient from worksheet 5 Ceqv

Soakage Rate (from worksheet 1) Sr _____ m/hr

Design storm

Duration I mm/hr

Depth (d) mm Q=CIequivAlot_/3600000 m3/s

Volume in Vin=(d/1000) x A m3

5 min

10 min

20 min

30 min

60 min – 1 hr

2 hr

6 hr

12 hr

24 hr

48 hr

72 hr

Note for soakage design initially use a one hour storm duration

Rainfall Runoff Volume 𝑅𝑐 = 10 𝑥 𝐶𝑒𝑞𝑖𝑣 𝑥 𝐼 𝑥 𝐴𝑙𝑜𝑡1000

= 10 x ___ x ___ x ___

Rc = _____m3

For a typical soakhole 900 mm diameter

Volume of runoff disposed of by 𝑉𝑠𝑜𝑎𝑘 = 𝐴𝑠 𝑥 𝑆𝑟 𝑥 𝑆𝑑

Design Templates




soakage

𝐴𝑠 = 𝑆𝑜𝑎𝑘𝑎𝑔𝑒 𝐴𝑟𝑒𝑎

(for one 900 mm dia soakhole) = 0.636 m2

𝑆𝑟 = 𝑆𝑜𝑎𝑘𝑎𝑔𝑒 𝑅𝑎𝑡𝑒

____ m/hr

𝑆𝑑 = 𝑆𝑡𝑜𝑟𝑚 𝐷𝑢𝑟𝑎𝑡𝑖𝑜𝑛

1 hr

𝑉𝑠𝑜𝑎𝑘 = 0.636 𝑥 _____𝑥1 _______m3

Volume of runoff held in storage 𝑉𝑠𝑡𝑜𝑟𝑒 = 𝐴𝑠 𝑥 𝐷𝑠 𝑥 𝑉𝑟𝑓


(for on 900 mm dia soakhole) = 0.636 m2

𝐷𝑠 = 𝐷𝑒𝑝𝑡ℎ 𝑜𝑓 𝑠𝑡𝑜𝑟𝑎𝑔𝑒 (ground water depth – 0.5 m or depth of soakhole - 0.5 m) Keep to 2.0 m max depth)

____m

𝑉𝑟𝑓 = 𝑉𝑜𝑙𝑢𝑚𝑒 𝑅𝑒𝑑𝑢𝑐𝑡𝑖𝑜𝑛 𝑓𝑎𝑐𝑡𝑜𝑟

0.38 for rock filled hole

𝑉𝑠𝑡𝑜𝑟𝑒 = 0.636 𝑥 __𝑥 0.38 _______m3

For 1 Soakhole Capacity = 𝑉𝑠𝑜𝑎𝑘 + 𝑉𝑠𝑡𝑜𝑟𝑒 _______m3

For the site Soakholes required - 𝑉𝑠𝑜𝑎𝑘 + 𝑉𝑠𝑡𝑜𝑟𝑒 > 𝑅𝑐

Therefore 𝑅𝑐𝑉𝑠𝑜𝑎𝑘+𝑉𝑠𝑡𝑜𝑟𝑒

=

_________ Soakholes

Design Templates




For a typical soak trench (1.0 m wide by 1.5 m long)

Volume of runoff disposed of by soakage

𝑉𝑠𝑜𝑎𝑘 = 𝐴𝑠 𝑥 𝑆𝑟 𝑥 𝑆𝑑


(1.0 m * 1.5 m) = 1.5 m2


____ m/hr


1 hr

𝑉𝑠𝑜𝑎𝑘 = 0.636 𝑥 _____𝑥1 _______m3



(1.0 m * 1.5 m) = 1.5 m2

𝐷𝑠 = 𝐷𝑒𝑝𝑡ℎ 𝑜𝑓 𝑠𝑡𝑜𝑟𝑎𝑔𝑒 (ground water depth – 0.5 m or depth of trench - 0.5 m) Keep to 2.0 m max depth)

____m



𝑉𝑠𝑡𝑜𝑟𝑒 = 0.636 𝑥 __𝑥 0.38 _______m3

For 1 trench Capacity = 𝑉𝑠𝑜𝑎𝑘 + 𝑉𝑠𝑡𝑜𝑟𝑒 _______m3

For the site Metre of trench required - 𝑉𝑠𝑜𝑎𝑘 + 𝑉𝑠𝑡𝑜𝑟𝑒 > 𝑅𝑐


=

_________ m

For proprietary system (dimensions and void figures from manufacturer) (use a 1.0 m length)




= __________m2


____ m/hr

𝑆𝑑 = 𝑆𝑡𝑜𝑟𝑚 𝐷𝑢𝑟𝑎𝑡𝑖𝑜𝑛 1 hr

Design Templates




𝑉𝑠𝑜𝑎𝑘 = _____ 𝑥 _____𝑥1 _______m3



______m2

𝐷𝑠 = 𝐷𝑒𝑝𝑡ℎ 𝑜𝑓 𝑠𝑡𝑜𝑟𝑎𝑔𝑒 (ground water depth – 0.5 m or depth of unit - 0.5 m) Keep to 2.0 m max depth)

____m


0.__________

𝑉𝑠𝑡𝑜𝑟𝑒 = ______ 𝑥 _____𝑥 _____ _______m3


For the site Metre of product required - 𝑉𝑠𝑜𝑎𝑘 + 𝑉𝑠𝑡𝑜𝑟𝑒 > 𝑅𝑐


=

_________ m

Summary of Calculations Soakhole ____m deep = ______ Soakholes 1.0 m x 1.5 m Soak trench _____deep = ______ metres of trench Proprietary system ______ deep = ______ metres of product

Design Templates

Worksheet 6 Detention Tank Design

W4.6 Infrastructure Technical Specifications


Site Address:

Completed by: Date:

Area for lot number ___ from worksheet 5 Alot__ _____ m2

Equivalent Runoff Coefficient from worksheet 5 Ceqv

Soakage Rate (from worksheet 1) Sr _____ m/hr

Design storm

Duration I mm/hr

Depth (d) mm Q=CIequivAlot_/3600000 m3/s

Volume in Vin=(d/1000) x A m3

5 min

10 min

20 min

30 min

60 min – 1 hr

2 hr

6 hr

12 hr

24 hr

48 hr

72 hr

Note for soakage design initially use a one hour storm duration

Rainfall Runoff Volume 𝑅𝑐 = 10 𝑥 𝐶𝑒𝑞𝑖𝑣 𝑥 𝐼 𝑥 𝐴𝑙𝑜𝑡1000

= 10 x ___ x ___ x ___

Rc = _____m3

For a typical soakhole 900 mm diameter

Volume of runoff disposed of by 𝑉𝑠𝑜𝑎𝑘 = 𝐴𝑠 𝑥 𝑆𝑟 𝑥 𝑆𝑑

Design Templates




soakage


(for one 900 mm dia soakhole) = 0.636 m2


____ m/hr


1 hr

𝑉𝑠𝑜𝑎𝑘 = 0.636 𝑥 _____𝑥1 _______m3



(for on 900 mm dia soakhole) = 0.636 m2

𝐷𝑠 = 𝐷𝑒𝑝𝑡ℎ 𝑜𝑓 𝑠𝑡𝑜𝑟𝑎𝑔𝑒 (ground water depth – 0.5 m or depth of soakhole - 0.5 m) Keep to 2.0 m max depth)

____m



𝑉𝑠𝑡𝑜𝑟𝑒 = 0.636 𝑥 __𝑥 0.38 _______m3

For 1 Soakhole Capacity = 𝑉𝑠𝑜𝑎𝑘 + 𝑉𝑠𝑡𝑜𝑟𝑒 _______m3

For the site Soakholes required - 𝑉𝑠𝑜𝑎𝑘 + 𝑉𝑠𝑡𝑜𝑟𝑒 > 𝑅𝑐


=

_________ Soakholes

Design Templates




For a typical soak trench (1.0 m wide by 1.5 m long)




(1.0 m * 1.5 m) = 1.5 m2


____ m/hr


1 hr

𝑉𝑠𝑜𝑎𝑘 = 0.636 𝑥 _____𝑥1 _______m3



(1.0 m * 1.5 m) = 1.5 m2

𝐷𝑠 = 𝐷𝑒𝑝𝑡ℎ 𝑜𝑓 𝑠𝑡𝑜𝑟𝑎𝑔𝑒 (ground water depth – 0.5 m or depth of trench - 0.5 m) Keep to 2.0 m max depth)

____m



𝑉𝑠𝑡𝑜𝑟𝑒 = 0.636 𝑥 __𝑥 0.38 _______m3


For the site Metre of trench required - 𝑉𝑠𝑜𝑎𝑘 + 𝑉𝑠𝑡𝑜𝑟𝑒 > 𝑅𝑐


=

_________ m

For proprietary system (dimensions and void figures from manufacturer) (use a 1.0 m length)




= __________m2


____ m/hr

𝑆𝑑 = 𝑆𝑡𝑜𝑟𝑚 𝐷𝑢𝑟𝑎𝑡𝑖𝑜𝑛 1 hr

Design Templates




𝑉𝑠𝑜𝑎𝑘 = _____ 𝑥 _____𝑥1 _______m3



______m2

𝐷𝑠 = 𝐷𝑒𝑝𝑡ℎ 𝑜𝑓 𝑠𝑡𝑜𝑟𝑎𝑔𝑒 (ground water depth – 0.5 m or depth of unit - 0.5 m) Keep to 2.0 m max depth)

____m


0.__________

𝑉𝑠𝑡𝑜𝑟𝑒 = ______ 𝑥 _____𝑥 _____ _______m3


For the site Metre of product required - 𝑉𝑠𝑜𝑎𝑘 + 𝑉𝑠𝑡𝑜𝑟𝑒 > 𝑅𝑐


=

_________ m

Summary of Calculations Soakhole ____m deep = ______ Soakholes 1.0 m x 1.5 m Soak trench _____deep = ______ metres of trench Proprietary system ______ deep = ______ metres of product

Design Templates

Worksheet 7 Combined Detention / Retention Tank

Design



Site Address:

Completed by:

For single dwellings detention tanks shall provide a minimum of _______ storage for re-use and the volume determined above for detention.

For multi-unit development detention tanks shall provide a minimum of _______ storage for re-use and the volume determined above for detention.

Inspection Templates

Wetlands and Dry Detention Basins Management Manual Checklist



Location: ________________________________________________________________________________________

Developer Council Comments Tick if correct Tick if correct

Administration Details

Developer name and contact details

Detention facility location – street address

Detention facility type (wetland, dry detention basin)

NZ map reference

Site plan No

Resource consent number (HCC and WRC)

Catchment name

Contributing catchment area

Coordinates for detention facility centre

Levels Levels to LINZ datum

Top of dam (RL)

Top of spillway (RL)

Toe of dam (RL)

2 yr ARI water level 10 yr ARI water level 100 yr ARI water level

Dimensions

Max pond length

Max pond width

Height of dam in metres to 0.1 m

Approx. max water depth to 0.1 m

Normal water depth to 0.1 m

Operating surface area (m2)

Normal storage volume (m3)

Spillway details Type Width or diameter

Inlet details Type Width or diameter

Outlet details Type Width or diameter

Flow Design 2 yr return period design m3/s 10 yr storm controlled at high level weir (m3/s) 100 yr storm at spillway (m3/s) Sediment Treatment Estimated suspended solids removal %

Estimated sediment accumulation rate in tonnes/year


Wetlands and Dry Detention Basins Management Manual Checklist



Developer Council Comments

Tick if correct Tick if correct

Safety Features

Planting details Date of planting Plants source Maintenance Requirements Methodology for the on-going and long-term maintenance Estimated cleaning frequency in years

• Forebay • Main pond

Details for permanently wet areas Details for surrounding areas How facility should be dewatered and desilted Attachments Location map Legal description of site Detailed scale plan of total contributing catchment Construction detail plans of the pond including all structures

Approved As-built plan showing truck maintenance access, working and storage areas

WRC resource consent Geotechnical report if applicable Design calculations As-built planting plan Consent compliance reports from WRC All information included in required format

Further information required

…………………………………………….. …………………………………………….. Developer Council …………………………………………….. …………………………………………….. Date Date


Wetland and Dry Detention Basin Inspection/Signoff Checklist



For completion by Developer prior to requesting:

1. 224c approval 2. First defects liability inspection 3. Final defects liability inspection 4. Remedial works completion inspection

Location: _________________________________________________________________________________________

Plan No. : __________________________

Date

Date Date Date

Type of Inspection (record 1,2,3 or 4)

Tick if satisfactory Tick if satisfactory Tick if satisfactory Tick if satisfactory

Pre-inspection 1) Final as-built plans sent to Council 2) Checklists completed for all pipelines and manholes 3) Planting Plan approved by Council Site Meeting 1) Forebay accessible and has all weather access 2) Forebay clear of sludge 3) Boundary pegs sighted 4) Works align with as built plans 5) Spillway/s clear of obstruction 6) Erosion and soil stability 7) Inlet and outlet has structural integrity 8) Plants at least 2.0 m clear of inlet and outlet 9) Planting done to approved planting plan 10) Plant density (approx. 1 per m2) 11) Plants in good condition 12) No plant pests 13) Weed (%) compliant with ITS 14) No notifiable weeds 15) Plants sourced from Waikato Ecological District

16) Safety Features All works satisfactory Remedial work required ………………………………….. …………………………………. Developer Council Date ……………………………

Date…………………………….

Quality Assurance Design Certificate


Version : October 2012 Page 1 of 1

WATER/WASTEWATER/STORMWATER – QUALITY ASSURANCE DESIGN CERTIFICATE

Site Address/Project Name

Consent Number if known

Name of Designer

Designers relevant qualifications

I hereby confirm that the design of the water reticulation / wastewater provision / Stormwater provision for the above site has been designed in accordance with the following standard _________________________________

Engineering Exception Decisions

The following aspects of the design do not meet the requirements of the above standard. (Where standards are not met, please detail the alternative standard achieved).

Accepted Y N

Signed: Date:

Pipe Laying Checklist F4.11 Infrastructure Technical

Specifications

Version : October 2012 Page 1 of 1 For further information about this form, email [email protected]

WASTEWATER PIPE LAYING CHECKLIST

Location:

to

to

to

to

to

Pipe Laying Checks Pipe length (MH To MH)

• Trench Safety (a) Shield (b) Batter (c) Other

• Pipe size, quality, approved materials confirmed

• Set out checked • Surveyors name ________________ • Control points identified

• Foundation support • penetrometer results available • if under cutting required, note

chainage and CBR results.

• Record daily level check and confirm on grade

• Bedding type and surround material _______________________________

• Bulk Backfill material _______________________________

• Bulk backfill compaction (CBR results from pipe to ground level attached)

• Alignment – control points identified

Service connections

• All service connections in place, taped and staked

• Connections correctly located horizontally and vertically

• Connections to main correctly formed

• As-built measurements taken

• CCTV pipe inspection

________________________________________ ________________________________________

Developer Date

mailto:[email protected]

Manhole Checklist F4.12 Infrastructure Technical

Specifications


MANHOLE CHECKLIST

Location:

to

to

to

to

to

Manhole Construction Checklist

MH number

• Manhole size, quality, approved materials checked

• Set out /orientation

• Sealing strip between risers

• Benching • Height • alignment and cross section • half pipe lining (wastewater only) • Step recesses (if applicable)

• Flexible joints

• Cutting and plastering of connections

• Access details per drawings

• Step irons including epoxy to outside recesses

• Bedding type and surround

• Bulk backfill compaction (CBR results attached)

• No debris in pipelines

• Invert of pipes in and out

________________________________________ ________________________________________

Developer Date


Trench Backfill Compaction Test

Summary Checklist


Version: October 2012 Page 1 of 1 For further information about this form, email [email protected]

TRENCH BACKFILL COMPACTION TEST SUMMARY (attach individual test reports)

Location: __________________________________________________________________________________

Plan No: __________________________________________________________________________________

From MH ______________________________ to MH ___________________________________

Acceptance Criteria: _______________________________________________________________________

Tests by: ______________________________________________________________ (attached)

Analysis of Results

____________________________________________________________________________________________

____________________________________________________________________________________________

____________________________________________________________________________________________

Trench backfill completed satisfactorily

Trench backfill requires remedial work

________________________________________ ________________________________________

Developer Date


Stormwater and Wastewater

Catchpit Checklist Checklist



CATCHPIT CHECKLIST

Location:

Catchpit Construction Checklist

Catchpit Number

• Catchpit , type, size, quality, approved material checked

• Set out /orientation

• Location checked

• Depth of sump below outlet correct

• Cutting and plastering of outlet connection

• Floating debris baffle installed correctly

• Backfill compaction around pit checked

• Seating and plastering of surround and grate to sump barrel

• All silt and debris removed from sump

________________________________________ ________________________________________

Developer Date


Final Inspection Pipe Network Checklist F4.15 Infrastructure Technical

Specifications


FINAL INSPECTION FOR STORMWATER AND WASTEWATER NETWORKS

Location: _________________________________________ Plan No: _________________________

Pre-Meeting Tasks

Developer Checklist Council Pass Developer to verify prior to meeting: SW WW

1. All checklists completed

2. All lines flushed out 3. All required CCTV inspections carried out, reviewed and any re-work

completed.

4. All manholes checked (eg.infiltration, plastering)

5. Catchpits checked

6. All backfilling complete and tidied up

7. Pressure test completed and witnessed

8. Final as-built plans attached for approval

9. Inspection arranged with Council

Site Meeting

1. Inspect all lines

2. Inspect all manholes and catchpits

3. All manholes and catchpits set to level

4. Inspect SW inlet and outlet structures

5. Secondary flowpaths and detention ponds

6. Works on third party land completed to satisfaction of owner

7. Wastewater pumping station

8. Overland flow from adjoining properties not effected

9. All works satisfactorily

10. Remedial work required ________________________________________ ________________________________________

Developer Council

________________________________________ ________________________________________

Date Date



Last Updated: 3 December 2012

Appendix B Drawings

Drawing No. Title

D4.1 Bubble Up Pit

D4.2 Kerb Connection

D4.3 100mm Dia. Stormwater Outlet

D4.4 Stormwater Secondary Flow Path Treatment – Private Property

D4.5 Groundwater Recharging Devices

D4.6 Footpath Berm Catchpit Details

D4.7 Catchpit Back Entry Details

D4.8 Double Sump Catchpit Design

D4.9 Vertical Entry Catchpit

D4.10 Aluminum Symbols for Catchpits

Version: JULY 2012

300

300

300

A

in cast iron frame

Cast iron swing grate

mm inlet

Nominal 90

K&C

vehicle cutdownChamber location in

CHAMBER PLANSECTION A

SITE PLAN

400mm or 600mm deep

Available chamber depths

300x300 ID concrete chamber.

LONGITUDINAL SECTION

Gutter

House

Stormwater Pipe

Flow

BoundaryDownpipe

CrossingVehicle

Roadway

500

GL (Driveway)

Min. 1200 deep

Chamber for 100Ø outlet800mm x 300 ID Concrete

outlet as D6.8Double catchpit for 225Ø as D6.9 for 150Ø outlet. Single catchpit generally

450 Min.

700

Min.

Min.

300

SN8 in berm

berm (Min.)SN8 in

K&C

Grass Berm

Footpath

Roadway

House

Stormwater pipe

D4.1

City Council

INFRASTRUCTURE TECHNICAL SPECIFICATION

BUBBLE UP PIT

Version: JULY 2012

D4.2

Road Reserve

Boundary

epoxy mortarReinstate kerb with Kerb and channel Footpath if present

to channel invertpipe kerb connection Cast galvanised steel

height (125mm)uPVC pipe for standard kerb 100mm x 50mm square box

to down pipe systemconnection according Square or round

Private drainage system

300

City Council


1m clear of vehicle crossings.3.

Grade 1 in 100.2.

to private drainage system.

standard if not immediately connected

Connection capped and pegged as per1.

NOTES:

KERB CONNECTION

Version: JULY 2012

Water Level

clear of norm

al flo

w

Base of outlet

100mmØ SN16 uPVC

material (preferably rip rap, concrete or rock)Hardening of bank required anti-scour

100mm spacings

20mmØ holes at

Glued or screwedFactory "T"

SN16 uPVC

100mm Ø

D4.3

City Council


100mm DIA STORMWATER OUTLET

Version: JULY 2012

50mm Min. 75mm Max.

Gap for flow under fence

H5 200 X 50

100

mm

50

mm

600

mm Min.

1500mm MIN.

Boundary

100

mm

Note 1

@ 2.4m Spacing (Max.)

: >1.5 m/s Hardening is required

: 1.0 - 1.5 m/s reinforcing is required

: < 1.0 m/s grass cover is sufficientFor 10 year ARI flow velocities1.

NOTE:

D4.4- PRIVATE PROPERTY

STORMWATER SECONDARY FLOW PATH TREATMENT

City Council


Version: JULY 2012

K&

C

SITE PLAN

RECHARGING DEVICES

GROUNDWATER

LONGITUDINAL SECTION

Gutter

House

Stormwater Pipe

Downpipe

sealed surfaceGrate inlet for

House

D4.5

overland flow pathTo connection or

Porous well liner

Porous well liner

Porous well liner

Downpipe

Downpipe

ConnectionStormwater

Council Storm

water

with overflowSoakage Catchpit

City Council


Version: JULY 2012

FOOTPATH BERM CATCHPIT DETAILS

Footpath

2500 radius (approx.)

Invert

PLAN

SECTION

Footpath dish channel in berm.

225Ø RCRRJ pipe. See Note 1.Cast iron grate to fit socket of

200 200

700 Min.

500 Min.

200

Footpath

1500 (Typical)

In-situ concrete base

225

150

In-situ concrete apron

225Ø RCRRJ - class 4 pipe

1:100 grade (Min.)

Type HS2 bedding

150Ø uPVC pipe on

1500 (

Typical)

300

475

1500 400 1500

A347

A

-

D4.6

City Council


strength of 20MPa.

have a minimum 28 day

All in-situ concrete shall2.

below invert of dish channel.

and cast iron grate set 25mm

Top of 225Ø RCRRJ pipe1.

NOTES:

Version: JULY 2012

Concrete haunching

lip and kerb of channel

barrel adjacent line of both

10mm Plate across Catchpit

shaped to direct flowIn-situ concrete inside face

480 100

230

Carriageway

In-situ concrete

concrete sump675 x 450 precast

DETAIL

component see abovePrecast back-entry kerb

to match channel profileCatchpit grate and frame angled

Berm/Footpath

A

-

-

A

BACK ENTRY CATCHPIT

PRECAST KERB COMPONENT

SECTION C-CELEVATION

C

600 Min.

C

100 Min.

90 Min.

D4.7 CATCHPIT BACK ENTRY DETAILS

City Council


Version: JULY 2012

DOUBLE SUMP CATCHPIT DESIGN

PLAN

SECTION

kerb component

Precast back entry

(Perpendicular slots), for cycle routesAlternative cast iron grate configuration

KERB

CHANNEL

500 Steel plate

FALL

central over pipe)

(i.e. back of grate

300 to ID

(on upstream pit)

with no back-entry cavity

Precast kerb component

(Giant Kokopu) See D610

Degreased aluminium fish

on upstream pit only

component with no bar

Precast back-entry kerb

See D6.7

Construction details

See D6.9

Floatables baffle

WATER LEVEL

pipe outlet

precast unit

or 675 X 450

1800

RC pipe

225

150

150

450

700 Min.

400Cast insitu concrete base

600 Min.

D4.8

City Council


For details see D6.73.

strength of 20MPa

All in-situ concrete shall have a minimum 28 day2.

epoxy or approved equivalent.

Epoxy product to be "ramset epcon C6" 2 pot1.

Cast iron grate with parallel slots shown in drawing.

NOTES:

Version: JULY 2012

VERTICAL ENTRY CATCHPIT

SCALE 1:25

PLAN

SCALE 1:25

SECTION B-B

B

B

SCALE 1:25

SECTION A-A

A A

Not to Scale

soffit of outletbe level with baffle top to Floatables

Steel Sheet1.6mm Stainless

Grate and Frame

Catchpit Sump

epoxied into sump wallnut and spring washer, 6mm galvanised rods, to chamber wall with Floatables baffle fixed

with normal gradeGrate set flush

fixing fish icon. See D6.10Stiff brush clean prior to (Giant Kokopu)Degreased Aluminium Fish

FLOATABLES BAFFLE DETAIL

(perpendicular slots) for cycle routesAlternative cast iron grate configuration

precast unitor 675 x 450 600Ø Class 2

225mm ØMinimum outlet

Top of Kerb

alignmentmatch rod Holes to

Carriageway

1800

600 min

150

strength of 20MPa.All in-situ concrete shall have a minimum 28 day 3.

approved equivalent.Epoxy product to be "Ramset Epcon C6" 2 pot epoxy or 2.

Cast iron grate with parallel slots shown in drawing. 1.

NOTES:

Carriageway

Channel

Kerb

500

600

225

150

600 Min.

150

50

D4.9

City Council


Version: JULY 2012

ALUMINIUM SYMBOLS FOR CATCHPITS

70 - 80mm

220 m

m

Cast Aluminium GIANT KOKOPU

SO

AK A

WA

Y

BU

BB

LE U

P75mm75mm

D4.10

City Council


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