Engineering Code of Practice

7/21/2019 Engineering Code of Practice

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The Hastings District Council administers a land area of over 500,000 km2

on the east coast of theNorth Island of New Zealand. This land varies from high country farmland beside the Ruahine andKaweka Ranges, through rolling pastoral farmland to the Heretaunga Plains. Within this land area is

included the larger urban areas of Hastings and Havelock North, and a number of smaller urbansettlements such as Clive, and the coastal settlements of Haumoana, Te Awanga and Waimarama.

Subdivision and land use projects within the District will be influenced by many factors, including thelocation, size and complexity of the project. In recent years, the Hastings District Council has strivedto provide developers with the information necessary to undertake projects which will meet therequirements of the District Plan and the Resource Management Act.

This Engineering Code of Practice is a comprehensive document which provides guidelines on theengineering standards Council will use when setting conditions for Resource Consents forSubdivision and Land Use projects. The Code does not aim to provide cookbook solutions. Thestandards in the Code provide acceptable solutions, but not necessarily the only solutions, for theengineering issues associated with subdivision and land use projects.

The Hastings District Council hopes that the Code of Practice will be widely used, and will assistdevelopers to complete projects which will benefit the District as a whole.

David FraserEngineering ManagerHastings District CouncilNovember 1997

Foreword


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HASTINGS DISTRICT COUNCIL : ENGINEERING CODE OF PRACTICEPART 2 : ENGINEERING STANDARDS

Contents

The Contents of Part 1 are as follows:

page

1.1 Introduction and Objectives 2

1.2 Structure of this Code of Practice 2

1.3 Relationship Between this Code and the District Plan 3

1.4 Relationship Between this Code and the Building Act 3

1.5 A Typical Land Development 4

1.6 How this Code Helps when applying for a ResourceConsent, or Land Use Consent

4

1.7 Effects Checklists 4

1.8 Information Requirements for Land Development andSubdivision

10

An Introduction to thisCode of Practice


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1.1 Introduction and Objectives

This Code of Practice is a document which the Hastings District Council hopes will :

Assist Developers to assess their obligations, responsibilities and liabilities on engineering issuesbefore embarking on a subdivision or land development project, or building project in the HastingsDistrict.

Assist Developers to determine the engineering design standards and performance targets thatmust be achieved in order to meet the conditions set by Council for the development of newfacilities in the Hastings District, in accordance with the Hastings District Plan.

Help Council to maintain a consistent, fair and flexible approach to the appraisal of developments.

Encourage innovation in development projects so that Hastings District benefits from theentrepreneurial skills of its people.

Council intends that the Engineering Code of Practice will be:

applicable to all land and infrastructure development within the District, including:

1) Subdivision Consents - By providing a set of Engineering Standards to enable compliancewith the rules for subdivision activities in the District Plan, and toidentify standards which developers may be required to comply withas a condition of a subdivision consent.

2) Land Use Consents - By providing a set of Engineering Standards to

enable compliance with the rules for land use activities in the DistrictPlan, and to identify standards which developers may be required tocomply with as a condition of a land use consent.

3) Building Consents - By providing a set of conditions for the supply of services inaccordance with the requirement of the Building Act as part of theProject Information Memoranda.

an end-product based document that requires developers to document each phase of theproposed development and to certify, through appropriately qualified professionals, any work thatis put to Council for acceptance, either as a public or private asset, in accordance with therequirements of the District Plan or the Building Act.

a living document which will be revised as technology changes.

1.2 Structure of this Code of Practice

This Code of Practice is presented in two parts;

Part 1 - provides an introduction to the Code, and describes the relationship between the Code,the District Plan and the Building Act.

Part 2 - provides the Engineering Standards. This part is presented in seven technical sections.


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1.3 Relationship Between this Code and the District Plan

The purpose of the District Plan is to assist the Hastings District Council to carry out its statutoryfunctions in accordance with the Resource Management Act, 1991. The Council has the responsibilityfor the integrated management of the effects of subdivision and land development activities, and thecontrol of those effects on the environment.

In the Hastings District Plan, there is a clear separation between the Objectives, Policies andMethods for addressing the effects of subdivision and development activities (these being containedwithin the District Plan) and the Engineering Standards used when setting conditions for consent(these being contained in the Engineering Code of Practice).

This Code of Practice is not a part of the District Plan. The Code describes engineering standardswhich Council believes provide acceptable solutions, but not necessarily the only solutions, for theengineering works associated with subdivision and land development. Council will impose conditionson Resource Consents, using the Code of Practice as a reference document for acceptablesolutions. These conditions will be enforceable through the rules in the District Plan. If a developerwishes to use engineering solutions or standards other than those described in the Code, these willneed to be fully justified by an appropriately qualified professional, in the Resource ConsentApplication.

1.4 Relationship between this Code and the Building Act

The Building Act came into effect on 1 July 1992. It established a new system of building control, andincludes a new Building Code which is more flexible and significantly different from the previousbylaw system. All elements of building are brought into the scope of this Act. The Building Consent isthe focus for all technical building matters.

This Code of Practice provides the builder and building owner with information on the EngineeringStandards that Council will use when setting conditions for building consent, on topics such as:

land stability

vehicle access

road development

services such as water supply, stormwater and sewage

and Councils requirements regarding the connection of services in a subdivision or land

development to existing Council services.

This Engineering Code of Practice does not provide specific technical information relating to buildingworks, such as plumbing, drainage, structural design, electrical standards or painting and decorating.


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1.5 A Typical Land Development

Before embarking on a description of how to use this Code, we will consider a typical developmentproject in terms of the requirements of both the Resource Management Act and the Building Act.Even though interpretations of these Acts can vary, the Hastings District Council believes that atypical medium sized subdivision development will follow the steps outlined in Figure 1.

1.6 How this Code Helps When Applying for a Resource Consent, or LandUse Consent

Figure 1 shows that the standards provided in the Engineering Code of Practice can be used severaltimes during a development. During the preparation of a Consent Application to Council, and duringEngineering Design and Construction, the Code will help developers to understand and the meetResource Consent Conditions. Because the scale of subdivisions and land development can vary

from, for example, a simple subdivision of two units, to a subdivision with many house units, servicesand roads, the amount of detail submitted with an application will also vary.

Applications for subdivision or land-use consents are required, by the Resource Management Act1991, to include an assessment of any actual or potential effects that the activity may have on theenvironment. An assessment also needs to be made of the ways in which any adverse effects maybe mitigated. The amount of detail submitted with an assessment must correspond with the scaleand significance of the actual or potential effects that the activity may have on the environment. Theassessment must be prepared in accordance with the Fourth Schedule to the Act. Information on theFourth Schedule is available from the Council offices. Applicants will need to attach an assessmentof effects with their applications.

1.7 Effects Checklists

The following checklists outline some of the more common matters which a developer will need toconsider when preparing an assessment of the effects of subdivision or land use. The checklists arenot a comprehensive list. Applicants will still need to refer to the Fourth Schedule to the Act toensure that all relevant matters are addressed.

Before an application is submitted, the developer should have discussed the proposal with Council,and other relevant authorities e.g., Hawkes Bay Regional Council. These discussions, and theanswers to the Effects Checklist should help to identify any significant environmental effects.

Where a potential effect is likely to be significant, then the developer may seek the expertise of anexperienced professional to assist with preparing the assessment. This professional might be, forexample, a planner, a surveyor, geotechnical engineer, traffic engineer, or an engineer skilled in

aspects of public health engineering including water supply and sanitary sewerage.


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The following checklist is provided to assist applicants to prepare their assessment of any actual orpotential effects which the subdivision may have on the environment. The checklist identifies some of themost common matters which the assessment will need to address. Applicants should also refer to Rule15.1.8.3 of Section 15.1 of the District Plan (on Subdivision and Land Development) which specifies otherinformation which must be submitted with some subdivision consent applications.

A Description of Proposal

Has the proposal been adequately defined, including Property Information?

B Natural Hazards

Is the site located within a Natural Hazard Resource Management Unit?(See Section 12.3 of the District Plan).

Does the site, or any adjacent land, have any history or evidence of erosion,

falling debris, subsidence, slippage or inundation from any source?

Does the proposed subdivision involve any earthworks or landform changes?

Is the site adjacent to a gully or a steep slope?

Is the site within 20m of permanent or flowing ( even intermittent) water?

Has the site been used as a landfill area?

C Landscape Features, Coastal Areas and Natural Areas?

Is the site located within an Outstanding or Significant Landscape Area,

Coastal Area or Natural Area (See Section 12.2 of the District Plan).

Is the site located in a Rural-Residential Zone?

Is the site located in the Te Mata Special Character Zone?

D Heritage Sites or Objects

Does the site have any Waahi Tapu or Heritage sites or objects within it which are

identified in Sections 12.4 and 12.5 of the District Plan?

E Visual Effects

Is the arrangement or shape of the proposed allotment(s) in keeping with the

pattern of development on adjoining land?

What is the extent of any earthworks or removal of vegetation?

Will this or adjoining sites be affected by dust or other pollutants (spray)?

Are there any plans for revegetation or landscaping of the site?

Effects Checklist for Subdivision Consent Applications


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F Property Access/Traffic

Can safe and efficient road access be provided to the site?

Does the site front onto a State Highway?

Will the site generate any extra traffic, or change in traffic patterns?:

will any of the above effects be

- during construction only?

- when the development is completed?

- both?

G Water Supply

Can the site be connected to a reticulated water supply?

If so, does the reticulated water system have sufficient capacity to supply the

intended or potential land use activities, including fire fighting which could occur onthe site?

If a reticulated supply is not available, can water be found on the site?

Could the abstraction of water affect the water resource from which it is taken?

H Stormwater

Is the intended or potential use of the site likely to increase the amount of

stormwater runoff from the site?

If so, could this have any effect on any waterbodies, or on the stability of landwithin

or adjoining the site?

Does the site have the ability to connect to a reticulated stormwater disposal

system?

If so, does the reticulated system have sufficient capacity to accommodate

stormwater from the site?

I Wastewater

Where the site can be connected to a reticulated sewage disposal system,

does the system have sufficient capacity to accommodate effluent which will begenerated by the intended or potential land use activities on the site?

Where connection to a reticulated sewage disposal system is not available, what

type of on site treatment system is appropriate?

J Hazardous Substance

Will the site development require storing, using, transporting, or disposing of any

hazardous substances or contaminants?

Please include an assessment of the effects, prepared in accordance with the Fourth Schedule to theResource Management Act 1991, in your Subdivision Consent Application


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The following checklist is provided to assist applicants to prepare their assessment of any actual orpotential effects which the Land Use may have on the environment. The checklist identifies some of themost common matters which the assessment will need to address. Applicants should also refer to Rule15.1.8.3 of Section 15.1 of the District Plan (on Subdivision and Land Development) which specifies otherinformation which must be submitted with some subdivision consent applications

A Description of Proposal

Has the proposal been adequately described? You are more likely to get the

consent of neighbours (if this is required) if they fully understand your proposal.

B Noise

Is the proposal likely to generate any additional noise beyond the site boundary?

What methods are proposed to mitigate any noise?

Will any of the above effects be



- both?

C Smell, Dust and General Nuisance

Is any smell, dust or general disturbance ( spray) likely to be detectable within or

beyond the site boundaries? If so, how can the effects be mitigated? Will any of the above effects be



- both?

D Contaminants, Waste Disposal

Have the measures proposed for waste disposal been identified? This should

include the nature of wastes and volumes, the extent of any contaminants likely tobe discharged into air, ground or water, and possible options for the treatment anddisposal of wastes. The Hawkes Bay Regional Council needs to be consulted for

any necessary discharge permit.

Is the site located over the Heretaunga Plans Unconfined Aquifer (refer Section12.6

of the District Plan).

E Hazardous Substances

Are any hazardous substances to be held or used on the site. Have possible

risks to the neighbourhood or the environment been identified. Describe safetyprecautions to be taken, and contingency plans to be used in an accident. (SeeSection 14.4 of District Plan).

Effects Checklist for Land Use Consent Applications


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F Landscape and Visual Effects

Has a description been provided of the possible visual impact of buildings,

equipment, storage or parking areas, also earthworks, roads, removal of vegetationduring construction. What screening or landscaping is proposed to reduce anyimpact these may have.

Is the site located in an Outstanding or Significant Landscape Area, Coastal Area.

or Natural Area or within a Rural-Residential Zone or the Te Mata SpecialCharacter Zone? (Refer Sections 7.0, 11.1, 12.2 of the District Plan)

G Effect on the Neighbourhood including Socio-economic or Cultural Effects

Have any possible effects on the character of the area or on the community been

identified . Does the site or adjoining sites have particular cultural or historicsignificance. Are there any waahi tapu or sites with particular significance totangata whenua. You may need to consult the Marae Committee. (Refer toSection 12.4 of District Plan of Waahi Tapu Sites, and Section 12.5 on

Heritage Items and Trees).

H Effect on Animals or Plants or their Habitats?

Are any significant trees or native bush likely to be removed or altered? Does the

site provide a habitat for protected insects, animals or birds?

I Property Access/Traffic

Will the development generate any extra traffic, or change in traffic patterns?

Is the road, which the site fronts onto, of sufficient design and construction to

cater for the traffic which will be generated by the intended or potential land use

activities on site?

Does the proposed use require advertising signage?

Can safe and efficient road access be provided to the site?

Does the site front onto a State Highway?

Will any of the above effects be



- both?

J Water Supply

Can the site be connected to a reticulated water supply?

If so, does the reticulated water system have sufficient capacity to supply the

intended or potential land use activities which could occur on the site - also for firefighting purposes?

If a reticulated supply is not available, can water be found on the site?


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K Stormwater

Is the intended or potential use of the site likely to increase the amount of

stormwater runoff from the site?

If so, does the reticulated system have sufficient capacity to accommodate

stormwater which will be generated by the intended or potential land use activities

on the site?

If there is not a reticulated system - can stormwater be disposed to the ground.

What are the effects on land stability, effects on waterbodies (includingunderground water).

L Landform

Does the proposed land-use involve any earthworks or land form changes.

Will there be any effects on landscape?

Will there be any effects on land stability?

M Persons Likely to be Affected

Have persons likely to be affected by the application been identified and consulted?

Any changes to a proposal as a result of the consultation should be pointed out.

N Other Bodies to be Consulted

It may be necessary to discuss your proposal with other public bodies, or service

utilities such as Transit New Zealand, (if your property is on a State Highway), theHawkes Bay Regional Council or the Department of Conservation and Telecom,Enerco, Transpower, HB Power Limited. Have any requirements or conditions ofthese bodies been included.

Please include an assessment of the effects, prepared in accordance with the Fourth Schedule to the

Resource Management Act 1991, in your Land Use Consent Application


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1.8 Information Required For Land Development and SubdivisionThe responsibility and accountability for meeting the requirements of the District Plan lies with the

Developer.

For Council to be able to process an application for resource consent, and this includes theassessment of effects, an applicant must provide adequate information. This information must beprovided in accordance with Section 88(4) of the Resource Management Act 1991, or for subdivisionconsent, Sections 88(4) and 219.

Section 92 of the Resource Management Act 1991, allows the Council, in respect of subdivision orland use consents, to seek more information about an application. This additional informationprovides Council with a better understanding of the nature of the activity for which consent issought, the effects the activity will have on the environment, and/or the ways in which adverse effectsmay be mitigated. If further information is required, the Council may postpone:

(i) Notification of the application, or(ii) Determination of the application, or(iii) Hearing of the application.

Failure to submit information where it is required, can therefore result in the postponement of theconsent process.

Figure 1 has shown that at various stages in the subdivision/ land development process Council willrequire that information is supplied by the developer. To assist Developers, Council has defined anumber of points in the Consent Process where information and certification by an appropriateprofessional should be submitted, if this is required by the Conditions of Consent. These points aredescribed in Table 1.1 below. The developers advisors will be required to certify the various stagesof the work on forms provided in Appendix 4.0 of the District Plan. The requirements to submit this

information may be made in addition to those matters identified in Section 4.0 of the District Plan. Thissection sets out the information that must be submitted with a Subdivision or Land Use ConsentApplication.

Table 1.1 - Information Requirements in Subdivision/Land Development Process

Point in the Process whereinformation required

Description of information required Form Reference(refer Appendix 4.0

of the District Plan)

Application for ResourceConsent for Subdivision

Consent Application.

Preliminary Geotechnical Report

Form 4-1

Form 4-2

Resource Management Act(1991) Section 224

Compliance

Geotechnical Report

Engineering Design Report

Construction report (Note: this will include allQuality Control information required inSection 2.7 of the Code of Practice).

Form 4-3

Form 4-4

Form 4-5

Building Consent - BuildingAct 1992.

To accompany Building Consent Application. Form 4-6

Copies of the certification forms can also be obtained from Council upon request. The forms shouldbe completed and signed by an appropriately qualified professional.


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Proposed Hastings District Plan

Proposed November 1997 Section 4.0 : Information Requirements Page 1

Form 4-1To: Hastings District Council

Private Bag 9002HASTINGS

Statement of Professional Opinion As to

Ability of the Proposed Subdivision to Comply WithDistrict Plan Subdivision Standards(Submit with Consent Application)

Subdivision: ...............................................................................................................................................

Owner/Developer: .....................................................................................................................................

Location:....................................................................................................................................................

I .................................................................................................................................................................(full name)

of ...............................................................................................................................................................(address)

hereby confirm that:

1. I am a suitably qualified professional experienced in Land Subdivision work and was retainedby the owner/developer in that regard on the above subdivision. My qualifications are .................................................................................................................................................................

2. Site Assessments have been carried out under my direction and are described in my reportdated ...........................................................................................................................................

3. I am aware of the details of the proposed scheme of subdivision and of the general nature ofproposed engineering works as shown on the following drawings ...................................................................................................................................................................................................(Insert References to all drawings including dates of latest amendments)

4. In my professional opinion, I consider that the proposed subdivision can comply with allrelevant Zone subdivision standards and all relevant General or Specific Site PerformanceStandards of the District Plan. A full assessment of the effects of the subdivision has beencompleted in accordance with the Fourth Schedule to the Resource Management Act 1991and is included as a report which is attached to this form. I consider that the land is suitablefor the proposed subdivision providing that:

(Please provide details of any works needed to ensure compliance with the standards).

a. .................................................................................................................................................

b. .................................................................................................................................................

c. .................................................................................................................................................

This professional opinion is furnished to the Council and the owner/developer for their purposes alone,on the express conditions that it will not be relied upon by any other person and does not remove thenecessity for further inspection during the course of the works.

Signed : ........................................................................... Date: ........................................................


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Form 4-2

To: Hastings District CouncilPrivate Bag 9002HASTINGS

Statement of Professional Opinion As toSuitability of Land for SubdivisionPreliminary Geotechnical Report

(Submit with Consent Application)

Subdivision: ...............................................................................................................................................

Owner/Developer: .....................................................................................................................................

Location:....................................................................................................................................................

I .................................................................................................................................................................

(full name)

of ...............................................................................................................................................................(address)


1. I am a suitably qualified professional experienced in the field of Geotechnical Engineering andwas retained by the owner/developer in this regard on the above subdivision. Myqualifications are .........................................................................................................................

2. Site investigations have been carried out under my direction and are described in my reportdated ...........................................................................................................................................

3. I am aware of the details of the proposed scheme of subdivision and of the general nature ofproposed engineering works as shown on the following drawings ...................................................................................................................................................................................................(Insert References to all drawings including dates of latest amendments)

4. In my professional opinion, I consider that the proposed works give due regard to land slopeand foundation stability considerations that the land is suitable for the proposed subdivisionproviding that:

a. .................................................................................................................................................

b. .................................................................................................................................................

c. .................................................................................................................................................


Signed : ........................................................................... Date: ........................................................


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Form 4-3


Statement of Professional Opinion As to

Ability of the Subdivision to Comply WithSubdivision Consent Conditions for Geotechnical Works

Subdivision: ...............................................................................................................................................

Owner/Developer: .....................................................................................................................................

Location:....................................................................................................................................................

I .................................................................................................................................................................(full name)

of ...............................................................................................................................................................(address)


1. I am a suitably qualified professional experienced in the field of Geotechnical Engineering andwas retained by the owner/developer in that regard on the above subdivision. Myqualifications are .........................................................................................................................

2. Site Investigations have been carried out under my direction and are described in my reportdated ...........................................................................................................................................

3. I am aware of the details of the proposed scheme of subdivision, the conditions imposed by

Council on the subdivision Consent and of the general nature of proposed engineering worksas shown on the following drawings .................................................................................................................................................................................................................................................(Insert References to all drawings including dates of latest amendments)

4. In my professional opinion, I consider that the works have been completed in accordance withthe conditions of the subdivision consent for geotechnical works, providing that:

(Please provide details of any works needed to ensure compliance with the standards).

a. .................................................................................................................................................

b. .................................................................................................................................................

c. .................................................................................................................................................


Signed : ........................................................................... Date: ........................................................


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Form 4-4


Certification of EngineeringDesign for Subdivision

Subdivision: ...............................................................................................................................................

Owner/Developer: .....................................................................................................................................

Location:....................................................................................................................................................

I .................................................................................................................................................................(full name)

of ...............................................................................................................................................................(address)


1. I am a suitably qualified professional experienced in the field of ................................................and was retained by the owner/developer in that regard on the above subdivision. Myqualifications are .........................................................................................................................

2. Designs have been carried out under my direction and are described in my report dated ..............................................................................................................................................................

3. I am aware of the details of the proposed scheme of subdivision as shown on the followingdrawings, and the conditions imposed by Council. (I have also made reference to thefollowing reports in the Design) .........................................................................................................................................................................................................................................................

4. I certify that the Design done under my control has been carried out in accordance with theconditions of the Subdivision consent.

Please note the following special considerations:

a. .................................................................................................................................................

b. .................................................................................................................................................

c. .................................................................................................................................................

This certification is furnished to the Council and the owner/developer for their purposes alone, on theexpress conditions that it will not be relied upon by any other person and does not remove thenecessity for further inspection during the course of the works.

Signed : ........................................................................... Date: ........................................................


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Form 4-5


Certification of Construction and Completionof Engineering Works for Subdivision

Subdivision: ...............................................................................................................................................

Owner/Developer: .....................................................................................................................................

Location:....................................................................................................................................................

I .................................................................................................................................................................(full name)

of ...............................................................................................................................................................(address)


1. I am a suitably qualified professional experienced in the field of ................................................and was retained by the owner/developer in that regard on the above subdivision. Myqualifications are .........................................................................................................................

2. The Construction Works have been carried out under my observation and are described in myreport dated .................................................................................................................................

3. I am aware of the details of the proposed scheme of subdivision and the conditions imposedby Council as shown on the following drawings ..........................................................................

.....................................................................................................................................................(Insert references to all drawings including dates of latest amendments)

4. In my professional opinion, I consider that the proposed works have been constructed andcompleted in accordance with the conditions of the subdivision consent.

Please note the following special considerations:

a. .................................................................................................................................................

b. .................................................................................................................................................

c. .................................................................................................................................................

This certification is furnished to the Council and the owner/developer for their purposes alone.

Signed : ........................................................................... Date: ........................................................


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Form 4-6To: Hastings District Council

Private Bag 9002HASTINGS

Statement of Professional Opinion As toSuitability of Land for

Building Development

Subdivision: ...............................................................................................................................................

Owner/Developer: .....................................................................................................................................

Location:....................................................................................................................................................

I .................................................................................................................................................................(full name)

of ...............................................................................................................................................................(address)


1. I am a suitably qualified professional experienced in the field of Geotechnical Engineering andwas retained by the owner/developer in this regard on the above subdivision. Myqualifications are .........................................................................................................................

2. The extent of my inspections during construction, and the results of all tests carried out aredescribed in my report dated........................................................................................................

3. In my professional opinion, not to be construed as a guarantee, I consider that:

* a. The earth fills shown on the attached Plan No ...............................................................

have been placed in compliance with the Code of Practice of the Hastings DistrictCouncil.* b. The completed works give due regard to the land slope and foundation stability

considerations.* c. The filled ground is suitable for the erection thereon of residential buildings not

requiring specific design in terms of NZS 3604 and related documents providing that:

(i) ........................................................................................................................................(ii) ........................................................................................................................................(iii) ........................................................................................................................................

* d. The original ground not affected by filling is suitable for the erection thereon ofresidential buildings not requiring specific design in terms of NZS 3604 and relateddocuments providing that.

(i) ........................................................................................................................................(ii) ........................................................................................................................................(iii) ........................................................................................................................................

4. This professional opinion is furnished to the Council and the owner/developer for theirpurposes alone, on the express conditions that it will not be relied upon by any other personand does not remove the necessity for the normal inspection of foundation conditions at thetime of erection of any dwelling.

Signed ................................................................ Date ....................................................................

* Delete items not applicable


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Hastings District Council : Engineering Code of PracticePart 2 : Engineering Standards, Introduction

Hastings District Council - Code of Practice for Subdivision and Land Development

Part 2 Section 2.1November 1997 1

This Code of Practice provides guidelines for engineering standards which Council considers areacceptable solutions for Subdivision and Land Use projects in the Hastings District. These standardscan be applied during the investigation, design and construction of any development.

Part 2 of this Code of Practice is subdivided into six technical sections. These are:

The technical sections are colour coded and separately paginated to make them easier to use, eithertogether or individually. The front of each section contains a detailed Table of Contents. Referencesto published documents and standards are provided in all the Sections.

Section 2.1Introduction

Section 2.4 Sanitary Sewer

Section 2.2 Geotechnical Engineering

Section 2.3 Stormwater

Section 2.5 Water Supply

Section 2.6 Road and Traffic Engineering

Section 2.7 Contracts, Specifications, Quality Assurance and As-BuiltDocumentation


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Hastings District Council : Engineering Code of PracticePart 2 : Engineering Standards, Geotechnical Engineering



Contents

The Contents of this Section are as follows:

page

2.2.1 Introduction 2

2.2.2 Standards and Publications 2

2.2.3 Responsibility of the Developers in relation to Earthworks 3

2.2.4 Preliminary Geotechnical Report 3

2.2.5 Geotechnical Design Report 4

2.2.6 Guidelines for Specifications and Drawings 4

Section 2.2Geotechnical Engineering


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2.2 Geotechnical Engineering

2.2.1 Introduction

This section of the Code of Practice provides theEngineering Standards required for the geotechnicalissues associated with a Subdivision or LandDevelopment. Geotechnical issues may include thefollowing:

the earthworks associated with the excavation andfilling of land

the construction of stable slopes

the suitability of both natural and made ground forthe foundation of roads, buildings, services andother works.

the control of erosion during and after earthworks.

Because of the wide range of soil types, physical conditions and environmental factors experiencedin the Hastings District, it is not possible to set precise requirements which will be applicable in allcases. The criteria set out in this section are therefore intended as indicative standards only. It isexpected that if a Subdivision or Land Development involves earthworks, that the advice of anexperienced professional will be obtained.

2.2.2 Standards and Publications

If the proposed development involves significant earthworks (refer Section 2.2.3) the advice of anexperienced professional is required. Reference should also be made to the followingrecommended publications:

NZS 4431 : 1989 Code of Practice for Earth Fill for Residential Development

NZS 3604 : 1990 Code of Practice for Light Timber Frame Buildings not requiringspecific design (Parts 3 and 4 in particular)

NZS 4229 : 1986 Code of Practice for Concrete Masonry Buildings not requiringspecific design (Parts 3 and 4 in particular)

NZS 4402 : 1986 Methods of Testing Soils for Civil Engineering Purpose, Parts 1and 2

TNZ F/1 1986 Specification for Earthworks Construction

NZS 4404 : 1981 Code of Practice for Urban Land Subdivision

New Zealand Building Code, in particular Section B1


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DSIR Information Series No.122, January 1977, Slope Stability in Urban Development

2.2.3 Responsibility of the Developer in relation to Earthworks

Council will require that Developers take full responsibility for any land development or subdivisionthat may affect the existing landform. To ensure this, and with particular reference to thegeotechnical aspects of the project, the following reports will be required:

Preliminary Geotechnical Report - with Resource Consent Application or Building ConsentApplication.

Geotechnical Design Report - following Consent

As Built information, Quality Assurance Report and Certification - submitted for Section 224approval, or Code Compliance in accordance with Section 2.7 of this Code of Practice.

These reports are described in more detail below.

2.2.4 Preliminary Geotechnical Report

After the development of preliminary Scheme Plans, and prior to any detailed planning and design, aPreliminary Geotechnical Report will be required, (except if specifically exempted by Council) insupport of a Consent Application, where land development involves any of the following:

Earthworks - General

Total earthworks volume (cut plus fill) > 100m3, in-situ measure

Earthworks within designated hazard zones

Earthworks that significantly alter surface or subsurface drainage patterns

Excavation Excavations greater than 2.5 metres overall vertical extent

Excavations steeper than 2.5 Horizontal to 1 Vertical (22o)

Excavations on, or within ten metres of, existing slopes higher than 5 metres overall vertical extent

Excavations below the ground water table

Excavations the top of which are within 10 metres of buildings or surcharge loads

Fill

Buildings on fill or made ground

Fills on existing ground sloping steeper than 3.5H:1V (16o)

Fills constructed on, or within a zone extending above an angle of 3 Horizontal to 1 Vertical (18o)from, the toe of a slope or river bank

Fills within 10 metres of a building or the base of a slope Fills with a maximum depth greater than 1.5 metres

Fills with batter slopes steeper than a) 2H:1V (26o) in sand and gravelb) 3H:1V (18o) in silt and clay

Retaining Structures

Retaining walls higher than 1.5 metres overall vertical extent

Retaining walls with sloping backfill

Retaining walls with surcharge loading within three metres of top of wall


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The Preliminary Geotechnical report is to be prepared by an experienced professional. It willprovide a preliminary evaluation of the site in sufficient detail to determine the likely geotechnical

requirements of the proposed subdivision. The report must be submitted with the ConsentApplication application and will include:

(a) the results of any site investigations and material testing,

(b) the assessment of geological hazards,

(c) the geotechnical constraints on land development,

(d) the geotechnical recommendations for site development, for issues such as batter slopes,fill construction, drainage, erosion control etc.

(e) the identification of any requirements for additional investigations or analysis,

(f) the confirmation that a suitable building site is available on each lot,

(g) the confirmation that suitable vehicle access can be provided to each lot, and building site.

2.2.5 Geotechnical Design Report

The Conditions on a Resource Consent or Building Consent may require more detailed geotechnicalinvestigation and analysis where this is identified as being necessary in the PreliminaryGeotechnical Report, where the Resource Consent conditions require it, or where new issues ariseduring detailed design.

A Geotechnical Design report shall detail all investigations and design work carried out, conclusionsdrawn and recommendations made, and list any requirements for construction. Relevant topics mayinclude assessments of material types and use, foundation bearing capacity, lateral pressures onretaining walls, settlement, slope stability, required subsoil and surface drainage, fill compactionstandards for differing soil types, stormwater controls, septic tank effluent disposal (where relevant),batter slopes on fills and cuts, access road drainage controls and erosion protection etc.

2.2.6 Guidelines for Specifications and Drawings

If the earthworks associated with a subdivision or land development requires a constructionspecification Council will expect it to be prepared to a standard that ensures that all features of thedesign are properly understood and carried through to construction. The following information refersto specifications for earthworks. Reference should also be made to Section 2.7 of this Code of

Practice which provides a general overview of construction specifications.

A specification for workmanship and materials must be provided covering earthworks standards,methods of quality control to be achieved during construction and the systems of checking to beused in monitoring the works. Typically this will include :-

standards for stripping of the existing ground and removal of unsuitable materials

standards for the placing and for the quality of fill material

standards for cut slopes and benching if required

compaction standards (refer NZS 4431, 1989)


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geometric control of finished levels and position, including batter slopes

standards for earth reinforcement, and/or retaining wall construction, including foundations

dust control standards requirements for revegetation and/or landscaping of batters.

Quality Assurance Hold Points and inspection by the Certifying Engineer (refer NZS 4431, 1989Section 9).

Typically the drawings associated with an earthwork specification will include, but not be limited to:

the extent of cut and fill, batter slopes and heights, road subgrade geometry, and the extent andtype of subsoil drainage

the pre-construction and post construction contours including details of the drainage paths.

construction detail for retaining walls and/or earth reinforcement.

details of proposed silt control during construction.

details of culverts - size and alignment, inlet and outlet details, installation detail. As-built drawings of the above will also be required. Refer Section 2.7 of the Code of Practice,

and NZS 4431, 1989, Section 10.1.


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Hastings District Council : Engineering Code of PracticePart 2 : Engineering Standards, Stormwater

Hastings District Council - Code of Practice for Subdivision and Land DevelopmentPart 2 Section 2.3

November 1997 1

Contents

The Contents of this Section are as follows:

page

2.3.1 Introduction 2

2.3.2 Performance Criteria 2

2.3.3 Design Guidelines 3

2.3.4 Guidelines for Specifications 11

2.3.5 Inspection During Construction 15

2.3.6 General Requirements for Private Developers 16

Section 2.3Stormwater


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Hastings District Council - Code of Practice for Subdivision and Land DevelopmentPart 2 Section 2.3November 1997 2

2.3 Stormwater

2.3.1 Introduction

This section provides a set of Engineering Standardsfor the design and construction of stormwater drainagewithin subdivisions which are to come under HastingsDistrict Council (HDC) jurisdiction and/or ownership.The intention is to:

ensure stormwater drainage is designed andconstructed such that the subdivision meets thesurface water performance criteria of the NewZealand Building Code

provide guidance for effective supervision leading tohigh construction standards.

2.3.2 Performance Criteria

2.3.2.1 Capacity and Layout

A stormwater system shall:

a) Provide protection from floods of up to a 50 year return period ( 2%probability of exceedance ) using a system of primary and secondary flow paths,

appropriate to the intended land use.

b) Provide rural lots with an area suitable for effluent disposal that is free frominundation in a 10 year return period storm ( 10% probability of exceedance )

and not cause a health hazard during any inundation.

c) Adequately service the catchment and accommodate the design flows, for boththe level of development at the time of design and that which can reasonably beexpected to exist once the catchment is fully developed as allowed for under theDistrict Plan.

d) Adequately service each lot, road area or land area discharging to the point ofentry, to an approved outlet.

e) Wherever practical convey the flow by gravity.

f) Be compatible with the existing drainage network without any adverse effects onthe existing system, and on upstream and downstream properties.

g) Not cause undue restrictions on the location of any future building ordevelopment nor cause any undue risk to public health and safety.

h) Be designed and constructed to facilitate ongoing maintenance, minimize riskof debris or gravel blockage, outlet scour or land instability, and provide efficientand safe inlet and discharge.


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i) Enhance the amenity value of any open channels and flood banks withprotection from scouring, erosion or siltation.

j) Comply with all applicable Resource Consents and minimize adverse effects onthe environment.

k) Where practicable utilise mechanical, electrical, alarm and telemetry equipmentwhich is compatible with existing equipment used by HDC.

l) Ensure that mechanical and electrical equipment is either designed forsubmergence, or located above, the 100 year design flood level. ( 1% probabilityof exceedance )

2.3.2.2 Structural Integrity

A stormwater system shall:

a) Be constructed from approved materials suitable for that use, with a minimumdesign life of 80 years, and with a proven record of performance.

b) Not suffer damage from any anticipated superimposed load and ensure safetyduring operation of the system.

c) Minimize root penetration of piped systems and erosion, piping or collapse ofbatter slopes of open channels.

2.3.3 Design Guidelines

The following topics are included in the discussion of design guidelines:

2.3.3.1 The Stormwater System

2.3.3.2 Catchments

2.3.3.3 Stormwater Runoff

2.3.3.4 System Design

2.3.3.5 Pipeline Design

2.3.3.6 Open Watercourses

2.3.3.7 Inlet and Outlet Structures

2.3.3.8 Manholes

2.3.3.9 Connections

2.3.3.10 Sumps

2.3.3.11 Location of Pipelines


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2.3.3.12 Stormwater Pumping

2.3.3.13 Siphons

2.3.3.14 Vicinity of Other Services

2.3.3.15 Miscellaneous facilities

2.3.3.1 The Stormwater System

Stormwater drainage encompasses the total system protecting land and infrastructureagainst flooding. The primary drainage system consists of pipes and open channels,while overland flow paths and controlled flood plains provide additional protection (thesecondary system).

2.3.3.2 Catchments

All stormwater systems shall provide for the collection and controlled disposal ofstormwater from within the land being developed, together with any runoff from upstreamcatchments including roads and driveways etc. In designing downstream facilities theupstream catchment should be considered as being fully developed to the extentpermitted in the current District Plan under both present and deferred zonings.

For larger developments or where constraints exist in the downstream stormwatersystem, a developer may be required to ensure that the development creates noincrease in downstream storm flow. To satisfy this requirement the design of stormwaterattenuation will be required within the development catchment area. Specific attenuationmethods and design criteria shall be submitted to Council for approval with the Design

Report, (refer Part 1 of this Code of Practice).

2.3.3.3 Stormwater Runoff

Stormwater runoff from a catchment or watershed, above a particular element of thesystem being designed, should be calculated in accordance with the Rational Method orModified Rational Method. These methods are described in the New Zealand BuildingCode, Approved Document E1 - Surface Water. Alternative methods will be acceptedsubject to appropriate certification and approval by Council.

Rainfall intensities and duration for probabilities of exceedence of 2, 5, 10 and 50 yearreturn periods for the Hastings urban area are shown in Drawings 2.3.1 and 2.3.2. Datafor other areas can be obtained from Council, who will use the HIRDS, High IntensityRainfall Design System. Developers will be asked to provide Council with locationcoordinates for this system.Composite runoff coefficients for developed urban areas or land that is expected to bedeveloped as a residential area typically are:

0.5 for a 5 year return period rainstorm0.6 for a 50 year return period rainstorm

The values of runoff coefficient in Table 2.3.1 can also be used as a guideline for otherareas. Reference should also be made to the figures in the New Zealand Building Codewhen preparing a design.


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Table 2.3.1 Stormwater Runoff Coefficients

Zoning Return Period

5 Year 50 Year

Outer Residential 0.4 0.6

Inner Residential 0.5 0.65

Inner City Commercial 0.8 0.8

Industrial Heavy 0.5 0.6

Industrial Light 0.7 0.75

Parks 0.3 0.5

Sealed Surfaces 0.9 0.9

Flaxmere Residential 0.2 0.25

Flaxmere Commercial 0.4 0.5

Omahu Rd Industrial (shingle) 0.25 0.3

2.3.3.4 System Design

The primary stormwater system shall be pipes except where Council approves an openwatercourse (refer Section 2.3.3.6).

The primary stormwater drainage system of pipes and/or open watercourses shall havesufficient capacity to convey a 5 year rain storm without surcharging onto roads i.e., notwithin 400mm of kerb tops. If a detailed accurate runoff calculation method is applied, ahydraulic grade line 250mm below kerb level may be acceptable to the Council.

For rainfall in excess of a 5 year storm up to a 50 year rainstorm, the secondarystormwater system shall have sufficient capacity to discharge runoff and protectbuildings and household gully traps from inundation.

2.3.3.5 Pipeline Design

Pipes shall be sized according to Mannings formula or any other approved method.Council will require supporting calculations for submission with the Design Report (referPart 1 of this Code of Practice). Appropriate allowance shall be made for head losses atchanges of direction in manholes, refer Drawing 2.3.3.

The minimum flow velocity for pipes flowing just full shall be 0.7 m/s. Note that thechoice of a larger diameter pipe than is necessary for the peak discharge is not a

satisfactory means of achieving compliance with the minimum velocity requirements.

No stormwater pipe, except for a connection to a lot shall be less than 200mm internaldiameter.

All stormwater pipes shall be laid in accordance with the manufacturersrecommendations.

Pipeline plans shall show long-sections, identifying other crossing services (except watersupply laterals) and other drains with pipe diameters and invert levels.


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Pipewall strength shall be sufficient to withstand soil pressure, surface and traffic loads,and any other loads to be anticipated. These factors shall be taken into account during

design, and appropriately documented in the design report.

2.3.3.6 Open Watercourses

Open watercourses are discouraged as permanent features in urban areas.Consultation with Councils Drainage Engineer is required if alternative disposal methodsare not available.

Existing watercourses within a development or subdivision shall be protected by adrainage reserve or easement. The reserve or easement shall include clear landsufficient to allow access for maintenance purposes with the minimum bermrequirements shown in Drawing 2.3.4. Regional Council requirements shall also beconsidered in determination of access widths.

The extent of any stream or open watercourse improvement work shall be agreed withboth the Regional Council and HDC. Factors for consideration are:

the retention of natural topography and vegetation

hydraulics

maintenance requirements.

Where open watercourses are retained through a new development, channel upgradingand/or land raising may be required.

The design of open channels and secondary flow paths, e.g. parks, roads, paths anddrainage reserves, shall ensure that flow velocities will not induce erosion or scour.Where potential for scour or erosion exists preventative measures such as silt and debristraps, bank and bed protection, shall be included in the design. All overland flow pathsshall be identified and protected from conflicting uses and restrictions or obstruction.


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2.3.3.7 Inlet and Outlet Structures

Permanent structures shall be constructed at the inlets and outlets of pipelines.Provision shall be made for energy dissipation unless it is demonstrated that outletvelocities and in-situ bed and bank materials are such as to make this unnecessary. Thedesign shall ensure non-scouring velocities at the point of discharge. Inlet structuresshall be designed to develop sufficient head to overcome entry losses, and also satisfythe requirements of Section 2.3.3.4. For further reference see NZS 4404 Figure 12.

2.3.3.8 Manholes

General

Manholes shall be provided on all pipelines, at each change of direction and/orgradient, at each branching line of a diameter between 150mm and 600mm, at the

termination of mains, and at a spacing of not more than 90m. Manholes may beeither cast in situ or of precast concrete. Drawings 2.3.5 and 2.3.6 show preferredmanhole details.

Standard Manholes

Standard manholes are to be circular with an internal diameter of 1050mm and shallbe used on pipelines of depth more than 600mm.

Precast manholes shall consist of 1050mm internal diameter spun concrete pipe toNZS 3107 Class S with holes cast in the side for step irons. Riser sections shall bejointed as shown on the standard detail drawing, carried out in accordance with themanufacturers recommendations, to provide a watertight structure. The top riser is tobe made 300mm deep, to allow for easy lowering of the manhole barrel.

Cast in-situ manholes shall be constructed using ordinary grade concrete (20 MPa)vibrated to give maximum density and watertight construction.

Manholes on Large Pipelines

Manholes on pipelines where the use of a standard manhole is not suitable shall bespecifically designed to the approval of HDC. Manholes on straight sections ofpipelines of 1.2m diameter and larger may be constructed using pre-formed tees.

On pipelines 1m diameter and larger the spacing of manholes may be extended to200m and curvature on the pipeline may be permitted providing that joint deflectionsare within the limits of the manufacturers recommendations.

Deep Manholes

Manholes deeper than 5 metres shall be at least 1200mm in diameter and specificallydesigned for access and strength. Intermediate platforms shall be formed fromprecast manhole top slabs placed equidistant down the manhole such that themaximum spacing is 4.5m.


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Hydraulic Flow in Manholes

Losses in a manhole shall be compensated for by a drop in the invert across themanhole equivalent to 20mm plus 5mm per 10 of change in direction of flow, or asdetermined from a specific calculation. For a pipeline greater than 1m in diameter thedrop shall be determined by specific calculation.

Benching

The pipe invert and benching through manholes shall be as detailed in the standarddetail drawing. Edges shall be rounded and the benching given a form and finishwhich facilitates smooth flow, non-entrapment of debris, and easy access withcleaning rods.

Steps and Ladders

Manholes shall be provided with approved PE coated hot dipped galvanised steelstep irons. Step irons shall be of the dropper or safety type such that a foot will notslide off and shall be spaced at 300mm centres. For detailing see Drawings 2.3.5and 2.3.6.

Manhole Lids and Covers

Manhole lids and covers shall be as detailed in Drawing 2.3.5. Aluminium covers arenot permitted.

Manholes in Soft Ground

Where a manhole is to be constructed in soft ground the surrounding area shall beundercut down to solid ground and backfilled with suitable hardfill to provide anadequate foundation. Alternatively, subject to specific approval, the manhole shall beconstructed on a reinforced concrete base 150mm thick and twice the area of themanhole.

Pipe Connections to Manholes

On all rigid pipes (i.e. concrete or earthenware) entering and leaving manholes, aflexible joint must be provided as detailed in Drawings 2.3.5 and 2.3.6.

Drop Connections

Drop connections at stormwater manholes will not normally be required.

Manhole Requirements for Pipe Inter-Connections

Branch lines 300mm diameter and smaller may be saddled directly onto pipelines900mm diameter or larger, providing a manhole is supplied on the branching linewithin 50m of the main line.

Where a smaller diameter pipe is connected into a larger pipe the soffitts of the twopipes shall be set at equal height.


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2.3.3.9 Connections

Each residential stormwater connection shall be capable of providing drainage from thewhole building area of a lot (including all surface water from the yard), at grades andcover complying with the New Zealand Building Code. However, under specialconditions, and subject to certification by the designer and approval by Council of anadequate soakage system, the requirement to include the yard surface water in thecapacity of the connection may be waived. The certification from the designer shallinclude adequate proof that the soil and ground water on the lot can provide sufficientsoakage.

A connection laid to a residential lot shall end at least 500mm inside the boundary. Theconnection shall preferably discharge into the road channel but may be connected to amanhole, pipeline or road sump subject to approval. Pipes larger than 100mm diametershall discharge direct to a pipe, or enter the kerb via a back entry sump.

Where a connection is deeper than 1.8m below ground level, a ramped riser shall beconstructed to bring the connection to within 1.2m of ground level (refer Drawing 2.3.8).

The connection provided for each residential lot shall be capable of taking the spigot endof a 100mm nominal internal diameter PVC pipe.

Connections for commercial and industrial lots shall be designed to accommodate thedesign flow from the area served by the connection and meet the minimum requirementsfor stormwater as defined by the Building Act. Connections larger than 100mm diametershall be made directly to a main pipeline or road sump.

The end of each connection shall be marked by a 50mm x 50mm timber stake (treated

pine) with top painted green, extending from below invert level to 400mm above groundlevel. The end shall be sealed either by a factory sealed stopper or a plug fixed with arubber ring and held with stainless steel wire.

2.3.3.10 Sumps

Sumps shall be located as necessary (with a maximum spacing of 100m) to ensure thetotal design flow can enter the stormwater system without surcharging. The intakecapacity of a road sump with grating, back entry, and acceptable ponding, isapproximately 28 L/s. The preferred design for road sumps is discussed in Section 2.6.9Road Drainage.

Discharge from sumps shall be via pipe leads with a minimum diameter of 200mm, either

directly into manholes, or

soffit to soffit into a stormwater main of at least 600mm diameter, provided that thereceiving pipe has a manhole within 40m of the sump lead connection. Where thehydraulic gradient of a sump lead is affected by pipe full conditions in the main,specific design calculations to determine size will be required.

Sumps shall be sited so that they do not impede accessways or kerb crossings due toany ponding that may occur in heavy rainfall.


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Design consideration shall also be given to the effect of stormwater flows from and alongthe road surface, e.g. flow around corners and at intersections.

During road works or construction a suitable means of preventing detritus enteringsumps must be used. Any gravel or debris entering sumps or the stormwater systemshall be removed or flushed from the system prior to acceptance by HDC.

2.3.3.11 Location of Pipelines

In residential areas stormwater pipelines should be laid within the road reserve. Dueaccount should be given to location of other services, when defining pipeline alignments.Space limitations usually require that drainage pipes (sewer and stormwater) must belaid in the carriageway. If possible, drains shall be laid where access from the surface ispossible at all times. Pipelines shall not be laid within 500mm of kerb lines.

Pipelines on private land shall be sited to minimize reduction of the building areaavailable. Pipelines shall be laid at least 1.0m clear of existing buildings. Drainagestructures including manholes shall be located clear of boundaries and kerblines.

Stormwater pipelines shall be extended to the upper boundary of a subdivision unlessotherwise approved. Easements shall be provided for any public drainage on privateproperty.

2.3.3.12 Stormwater Pumping

Stormwater pumping will only be approved where gravity disposal is not feasible.

Pumping systems shall be specifically designed using a multi pump system to best

balance the need for regular pump operation against the relative infrequency of majorstorm events. Design philosophy and technical details shall be discussed with Councilbefore detailed design is commenced. All electrical equipment shall be designed for amaximum of 15 starts per hour.

All pumps within a station shall be of the same capacity. An additional installed pumpshall act as standby. Depending on the consequences of flooding during a pump stationpower outage, HDC may require that on-site emergency power generation be provided.

Valving of pumps shall be such that maintenance can be undertaken on the standbypump and check valve without interfering with the operation of the duty pump. Pipes of100mm diameter or larger shall be ABS, API Schedule 40 line pipe, concrete lined steel,ductile iron, or PVC material ( of appropriate Class); with all bends and valves

adequately protected against movement. Flanged or welded fittings shall be providedthroughout, with a proprietary dismantling joint or similar in the system to facilitatedismantling.

Stormwater pump stations shall incorporate control, monitoring, alarm and telemetrycommunication systems to HDC standards at the time of the design. Any station onprivate land must have all weather access for light trucks.

2.3.3.13 Siphon


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In exceptional circumstances inverted siphons may be acceptable, subject to theapproval of HDC.

2.3.3.14 Vicinity of Other Services

Where a stormwater pipe crosses another service pipe a minimum clearance of 150mmshall be maintained between the pipes. Due care must be given to proper compaction ofthe fill between and around the pipes. A smaller clearance will be accepted if the upperpipe is supported on a pedestal either side of the lower service pipe, as shown inDrawing 2.3.9.

2.3.3.15 Miscellaneous Facilities

Components of stormwater drainage systems which have not been specified may beproposed for use in stormwater drainage. Possible examples include stopbanks, dams

and spillways. Such items will be subject to the specific approval of HDC.

2.3.4 Guidelines for Specifications

2.3.4.1 General

The following clauses relate specifically to construction specifications which apply tostormwater works. Reference should also be made to Section 2.7 of this Code ofPractice which provides a general overview of construction specifications.

Specifications must clearly explain, in combination with the related constructiondrawings, the scope of works. They shall indicate the circumstances and conditions thecontractor may expect to face during the works and requirements the work shall complywith. While standard clauses may be used, the whole specification must be prepared andedited for each specific project.

The following topics are included in the discussion of guidelines for specifications:

2.3.4.1 General

2.3.4.2 Standards

2.3.4.3 Construction

2.3.4.4 Pipes

2.3.4.5 Joints

2.3.4.6 Cover to Pipelines

2.3.4.7 Pipe Strength, Bedding and Pipe Surrounds

2.3.4.8 Backfilling and Reinstatement

2.3.4.9 Testing of Stormwater Drainage System

2.3.4.10 Connection to HDC System


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2.3.4.2 Standards

The Standards and Codes of Practice which are listed below are referred to in thissection. The design, materials and methods of construction shall comply with thesestandards and codes as applicable. The standards shall incorporate the latestamendments. Standards superseding those listed shall automatically apply.

NZS 3107 Specification for Precast Concrete Drainage and Pressure Pipes

NZS 3109 Specification for Concrete Construction

NZS 3302 Specification for Ceramic Pipes, Fittings and Joints

NZS 4442 Welded Steel Pipes and Fittings for Water, Sewage and MediumPressure Gas

NZS/AS 3725 Loads on Buried Concrete Pipes

NZS 4452 Code of Practice for the Construction of Underground Pipe Sewersand Drains

NZS 7604 Specification for High Density Polyethylene Drain and Sewer Pipeand Fittings

NZS 7643 Code of Practice for the Installation of Unplasticised PVC PipeSystems

A/S NZS 1260 PVC pipes and fittings for drain, water and vent applications

2.3.4.3 Construction

All elements of a stormwater drainage system must be constructed in accordance withthe relevant New Zealand Standards, and with the specific requirements of the designprepared in accordance with this Code of Practice.

2.3.4.4 Pipes

The following pipe materials may be specified for use in the construction of stormwaterdrains provided they comply with the latest amendment of the New Zealand Standardcited.

Reinforced concrete pipes to NZS 3107(minimum Class X)

Ceramic pipes to NZS 3302

Concrete lined steel (CLS) to NZS 4442

Unplasticised PVC (uPVC) pipes to NZS 7649. Heavy Duty and Extra HD

High Density Polyethylene (HDPE) to NZS 7604

Corrugated Steel Pipe (CSP) to NZS 4405for culverts greater than 500mm diameteroutside urban areas

2.3.4.5 Joints

Where thermal expansion of the pipe may occur flexible joints capable of

accommodating the expected movement for a temperature rise of 25C shall be used.


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2.3.4.6 Cover to Pipelines

The following Table 2.3.2 gives the minimum cover to finished surface level above thecrown of pipes in different locations. Any design involving a cover less than the minimumshown, shall demonstrate that compliance is impractical and be supported with fullcalculations for approval.

Table 2.3.2 Minimum Ground Cover for Stormwater Pipes

Location Minimum Cover(mm)

Private property 375

Carriageways, driveways,road reserve, and parkingareas

750

Berms and paths 600

The designer shall check that in any particular case the surface load does not requiremore cover for the chosen pipe.

Where topographical conditions do not allow the prescribed cover to be achieved,reinforced or unreinforced concrete protection shall be provided over the pipelines to theapproval of HDC.

2.3.4.7 Pipe Strength, Bedding and Pipe Surround

Pipe strength and bedding shall be selected for suitability under the design loading

conditions. The type of bedding and class of pipe adopted shall be in accordance withNZS 4451and the appropriate pipe material standard, or the manufacturers pipe layingpublication.In general, with good ground conditions, bedding and other trench details shall be asshown in Drawing 2.3.10. Other designs may be accepted provided they are inaccordance with NZS 4451 and the appropriate pipe material standard, or themanufacturers pipe laying publication.

In poor ground conditions, potentially unstable ground, or where extreme loadings will beencountered; pipe strength and bedding shall be specifically designed and certified.

If the pipeline gradient is steep (generally not less than 1 in 10), and/or ground conditionsare poor, sufficient cement shall be added to the granular bedding material to provide a

weak concrete with a strength of not less than 7 MPa. The depth of bedding shall be asshown in Drawing 2.3.10, and shall be cleanly broken at the pipe joints with a 25mm gapformed with expanded polystyrene to maintain flexibility.

Where the pipeline gradient exceeds 1 in 10 anti-scour blocks shall be constructed asshown in Drawing 2.3.11 at the spacings shown in Table 2.3.3.

Table 2.3.3 Spacing of Anti Scour Blocks

Grade Spacing (m)

Steeper than 1 in 5 5


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1 in 5 to 1 in 10 10

Concrete and Ceramic

Backfilling pipe surround shall be carried out in general accordance with NZS 4452 for aType B pipe bedding. The selected fill (free of organic materials, lumps larger than75mm, and stones larger than 40mm) shall be placed in 150mm layers and compactedwith a hand operated vibrating compactor with a total static weight not exceeding 0.5tonne, to a density of not less than 95% of Maximum Dry Density as determined by NZS4402, Test 4.1.2..

All Other Pipes

Backfilling pipe surround shall be carried out in general accordance with Section 5 ofNZS 7643using granular bedding material as pipe surround to a minimum of 100 mm

above the top of the pipe.

Following placement of the pipe, the granular bedding material shall be placed in layersnot exceeding 150 mm and shall be carefully tamped with hand or mechanical tampers,with particular attention to compacting under the pipe haunches. The material shall notbe dropped from a height of greater than 600mm. The granular fill shall be compacted toa density of not less than 95% of the Maximum Dry Density as determined by Test 4.1.2of NZS 4402.

2.3.4.8 Backfilling and Reinstatement

When the pipe grade is less than 1 in 100 backfilling shall be free draining granularmaterial up to within 300mm of

Documents

Engineering Code of Practice