city of karratha town planning scheme no. 8karratha.wa.gov.au/sites/default/files/uploads/local...

CITY OF KARRATHA TOWN PLANNING SCHEME NO. 8

LOCAL SCHEME AMENDMENT

KARRATHA HIGH SCHOOL

LOT 4615 (RESERVE 30602) SEARIPPLE ROAD, BULGARRA

PREPARED BY

ON BEHALF OF

FEBRUARY 2016

City of Karratha

Local Scheme Amendment No. xxx

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LOCAL SCHEME AMENDMENT NO. xxx

TABLE OF CONTENTS

Resolution Deciding to Amend a Local Planning Scheme 4

Minister for Planning Proposal to Amend a Town Planning Scheme

5

SCHEME AMENDMENT REPORT

1.0 INTRODUCTION

6

2.0 SITE DETAILS

2.1 Property Location and Ownership 7

2.2 Existing Land Use 7

2.3 Surrounding Context 7

2.4 Topography 8

2.5 Access & Servicing 8

2.6 Potential Site Contamination 8

2.7 Indigenous and European Heritage & Native Title 13

2.8 Flooding 14

3.0 PLANNING CONTEXT

3.1 City of Karratha Town Planning Scheme No. 8 9

3.2 City of Karratha Local Planning Strategy 9

3.3 Karratha Revitalisation Strategy 9

4.0 PLANNING RATIONALE 10

5.0 SUBDIVISION CONCEPT PLAN 12

6.0 INFRASTRUCTURE & SERVICING

6.1 Wasterwater 14

6.2 Water Supply 14

6.3 Power 14

6.4 Telecommunications 14

6.5 Gas 14

6.6 Site Works 15

6.7 Roads 15

6.8 Stormwater Drainage 15

7.0 CONCLUSION 16

Resolution to Adopt a Local Planning Scheme & Scheme Amendment Map 17

SCHEME AMENDMENT MAP

18

FIGURES

Figure 1 Location Plan

Figure 2 Cadastral & Aerial Plan

Figure 3 Surrounding Context

City of Karratha


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APPENDICES

1 Certificate of Title

2 Preliminary Servicing Report

3 Subdivision Concept Plan

Adoption & Final Approval of Scheme Amendment 24

City of Karratha


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PLANNING AND DEVELOPMENT ACT 2005

RESOLUTION DECIDING TO AMEND A LOCAL PLANNING SCHEME

CITY OF KARRATHA

TOWN PLANNING SCHEME NO. 8

AMENDMENT No. xxx

RESOLVED that the Council, in pursuance of Section 75 of the Planning and Development Act 2005, amend the

above local planning scheme by:

1. Reclassification of Lot 4615 (Reserve 30602) Searipple Road, Bulgarra from Public Purposes -

Education local scheme reservation to Urban Development zone and amending the Scheme Map

accordingly.

The Amendment is complex under the provisions of the Planning and Development (Local Planning Schemes)

Regulations 2015 for the following reasons:

- The proposed scheme amendment seeks to reclassify land reserved under the Scheme for public

purpose in order to facilitate future urban development. The proposed reclassification is not identified

or provided for under the City of Karratha Local Planning Strategy.

Dated this _____ day of ________________ 2016

____________________________

Chief Executive Officer

City of Karratha


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MINISTER FOR PLANNING

PROPOSAL TO AMEND A TOWN PLANNING SCHEME

LOCAL AUTHORITY : City of Karratha

DESCRIPTION OF

TOWN PLANNING SCHEME : Town Planning Scheme No. 8

TYPE OF SCHEME : District Scheme

SERIAL NUMBER OF AMENDMENT : Amendment No. xxx

PROPOSAL : To reclassify Lot 4615 (Reserve 30602) Searipple Road,

Bulgarra from Public Purposes - Education to Urban

Development, to enable the subject land (excluding the

existing Primary School and Family Centre) to be

redeveloped to a suitable sequential land use,

consistent with the objectives and provisions of Town

Centre zone under TPS 8.

City of Karratha


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SCHEME AMENDMENT REPORT

1.0 INTRODUCTION

This report presents a proposal to initiate a Local Scheme Amendment to the City of Karratha Town

Planning Scheme No. 8 (TPS 8). The proposal seeks to reclassify Lot 4615 (Reserve 30602) Searipple

Road, Bulgarra from Public Purposes - Education local scheme reservation to Urban Development

zone.

The Karratha High School on the subject site is a redundant Western Australian Department of

Education asset and has been closed. Pupils have been relocated to the new Department of Education

public high school, which has been developed at the Karratha College Campus site.

The State Government has proposed to dispose of the subject site through the Land Asset Sales

Programme (LASP) process to the market. The proposal seeks to rationalise the public purpose

reservation use of the land by reclassification to the Urban Development zone under TPS 8.

The reclassification to Urban Development will provide opportunity to redevelop the site for a suitable

sequential land use, subject to the preparation and approval of a Structure Plan pursuant to Planning and

Development (Local Planning Schemes) Regulations 2015 Schedule 2 - Deemed provisions for local

planning schemes Part 4 Structure Plans. It is proposed that a Structure Plan is approved concurrently

with this local scheme amendment application.

City of Karratha


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2.0 SITE CONDITIONS

2.1 PROPERTY LOCATION AND OWNERSHIP

Lot 4615 (Reserve 30602) Searipple Road, Bulgarra (the subject site) is approximately 1.5km east of

Karratha town centre. The following is a table of the subject site details:

Lot Number Land details

Registered Proprietor

4615

Reserve 30602

Certificate of Title LR3110/961 Crown Land - State of Western

Australia

Management Order issued to

Minister for Education with

power to lease

Plan/Diagram Deposited Plan

193623

Lot Area 9.44ha

Figure 1 shows the location of the subject land in relation to the town of Wickham. Figure 2 shows the

cadastral boundaries and context of the subject site. The subject site Certificate of Title is contained in

Appendix 1.

2.2 EXISTING LAND USE

Lot 4615 is set aside as Crown Reserve 30602 with a Management Order issued to the Minister for

Education for use as Education. The former Karratha High School is located in the western portion of

the subject site, with school buildings in the south-west and the playing field in the north-west.

Currently the Karratha Primary School is situated within the south-east portion of the site and has

recently been upgraded. Within the north-western portion of the subject site is a family centre, which

has recently undergone refurbishment with additional landscaping upgrades. There is an existing utility

compound adjacent to the internal road off Searipple Road in the northern central portion of the subject

site. The primary school, utility and family centre are proposed to be retained as part of structure

planning, however the high school buildings and infrastructure is proposed to be demolished and

removed.

2.3 SURROUNDING CONTEXT

The subject site is bound on the western and eastern sides by Parks, Recreation and Drainage

reservation corridors (approximately 40m wide). Residential zoned land is the predominant

surrounding land use, with a density R-Code of R20. Surrounding established residential development is

predominantly detached single dwellings on 650m2

750m2

lots orientated north-south. Immediately to

the north on the opposite side of Searipple Road is undeveloped reserved land for Parks, Recreation and

Drainage and Conservation Recreation and Natural Landscapes, except for a Water Corporation

wastewater pumping stations and utility site. Further north is an existing short and long-stay

accommodation (Searipple Village) development. Figure 3 provides an overview of the surrounding

context.

City of Karratha


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2.4 TOPOGRAPHY

The subject site is relatively flat, with gentle undulations throughout. In general levels range between

7.0m AHD to 8.0m AHD across the site, with the highest point approximately 9.0m AHD in the south

and the lowest point approximately 6.0m AHD adjacent to Searipple Road in the north-west.

2.5 ACCESS & SERVICING

The subject site has direct frontage to Searipple Road and Turnery Way, both of which are sealed

roads. Services such as reticulated water, sewer, power and telecommunications are available.

A preliminary engineering servicing report (Appendix 2) has been prepared as a baseline investigation

ascertaining the feasibility for urban redevelopment, in particular, with reference to the Subdivision

Conept Plan (Appendix 3) included in this report. The findings of the engineering investigations

confirm that the subject site can be adequately serviced.

2.6 POTENTIAL SITE CONTAMINATION

A search of the Department of Environment Regulation Contaminated Sites Database indicates that

there are no recorded contaminated sites for the subject site.

2.7 INDIGENOUS AND EUROPEAN HERITAGE &NATIVE TITLE

Indigenous Heritage

A search of the Department of Indigenous Affairs Aboriginal Heritage Inquiry System indicates that

no Indigenous Heritage sites exist on the land.

Native Title

There are no outstanding Native Title claims affecting the subject site.

European Heritage

There are no places or sites of cultural significance within the subject site under the City of Karratha

Municipal Heritage Inventory and State Heritage Register.

2.8 FLOODING

The City of Karratha undertook a Coastal Vulnerability Study in August 2012. The study indicated that

2110 flood mapping affected some parts of the northern portion of the subject site. It is likely that

areas within the northern portion of the subject site will need fill. This is discussed further in section

6.0 of this report.

City of Karratha


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3.0 PLANNING CONTEXT

3.1 CITY OF KARRATHA TOWN PLANNING SCHEME NO. 8

Lot 4615 (Reserve 30602) Searipple Road, Bulgarra is currently reserved as Public Purposes -

Education local scheme reservation under TPS 8. If the subject site were reclassified to Urban

Development zone, the provisions of TPS 8 require a Development Plan (or Structure Plan) to be

prepared and approved. A Structure Plan would need to be prepared and approved pursuant to

Planning and Development (Local Planning Schemes) Regulations 2015 Schedule 2 - Deemed provisions

for local planning schemes Part 4 Structure Plans. It is proposed that a Structure Plan is approved

concurrently with this local scheme amendment application.

A Structure Plan would identify the future redevelopment area of the subject site, being an area which

excludes the area required for the existing Karratha Primary School and Family Centre. A suitable

curtilage would be provided in the Development Plan to incorporate the primary school and centre for

retention, with the balance land available for redevelopment.

At present, under Clause 2.2 of TPS 8, a person shall not carry out any development on a reservation or

change the use of a reservation without first applying for and obtaining the written approval of the City

of Karratha. As such, a prospective purchaser of the subject site could potentially apply for

development approval and seek the Citys discretionary development approval for a particular use. The

City could grant discretionary development approval after considering any development proposal on its

merits and taking into consideration Clause 2.2 and Clause 4.4 of TPS 8. However, to remove

uncertainty created by the existing local scheme reservation of the subject site, it is more appropriate to

reclassify the subject site to Urban Development zone, with an approved Development Plan. This

would provide the necessary planning framework and guidance for any future subdivision and/or

development approval for sequential redevelopment of the subject site.

3.2 CITY OF KARRATHA LOCAL PLANNING STRATEGY

The City of Karratha Local Planning Strategy identifies the future growth options for Karratha townsite.

However, the Strategy does not specifically identify the future redevelopment land use options for the

subject site.

3.3 KARRATHA REVITALISATION STRATEGY

The Karratha Revitalisation Strategy provides a guide for the future growth and development

opportunities for Karratha townsite. The Strategy identifies the subject site as relatively unconstrained for

future redevelopment, with retention of the existing primary school. The Subdivision Concept Plan

contained in this report is based on the conceptual redevelopment ideas for the subject site contained in

the Strategy. This will be further discussed in the report.

City of Karratha


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4.0 PLANINNG RATIONALE

The Department of Education and State Government has determined that the Karratha High School on

the subject site is now surplus to the States requirements and can be disposed as a freehold lot. This

will require conversion of the Crown Land into Freehold Title, excluding the existing Primary School and

Family Centre site.

A new high school facility has been developed at the Karratha College Campus site. Pupils have been

relocated to the new high school and the current former Karratha high school on the subject site has

been closed.

As an interim measure, security fencing has been provided around the former Karratha High School

facility. The Department of Education is required to continue on-going maintenance of the high school

buildings and grounds, until the site can be disposed. The Department of Education is seeking to

dispose of the high school land as soon as possible given that:

- The discontinued use of the high school buildings and grounds attract vandalism and anti-social

behavior; and

- The Department is required to finance the maintenance of the school buildings, playing fields

and grounds even though the high school is redundant and has been vacated.

The existing Karratha Primary School and Family Centre facility will be retained on a separate balance

reserve. The State Government has proposed to dispose of the surplus high school land through the

LASP process.

This proposed reclassification seeks to rationalise the public purpose reservation of the land by reclassifying

the land to the more appropriate Urban Development zone under TPS 8. The Urban Development zone

will provide opportunity to prepare and obtain approval for a Development Plan (or Structure Plan), which

can guide future land use under an appropriate statutory framework.

Aside from the land being redundant to Department of Education and State Government, the proposed

reclassification for the subject site to Urban Development is logical given that:

- The high school land is located within an established urban area, within the townsite of

Karratha, with access to existing roads, services and infrastructure;

- The high school land presents an opportunity for a relatively large urban infill development

project to occur, which can contribute to housing diversity and choice to accommodate

population growth;

- The potential high school land development site does not abut any private property, (i.e. there

are buffers, such as roads and open space, between the development site and existing

residences), therefore there will be limited impact on existing amenity;

- The requirements of the Urban Development zone for the preparation and approval of a

Structure Plan provides opportunity to plan for the delivery of a high quality residential

development, which would contribute to the amenity of the local neighbourhood and provide

land use diversity around the Karratha Primary School node;

City of Karratha


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- Redevelopment of the high school land is consistent with maximising efficient use of the urban

land, without compromising the residential amenity of the neighbourhood and

- The whole Lot 4615 (subject site) being reclassified to Urban Development as the Structure

Plan can identify the balance area containing the existing Primary School and Family Centre as

Public Purpose. The final balance area will be determined subject to structure planning,

feature survey and detailed subdivision design.

The surplus high school land includes an oval that is currently available as recreational open space for

the general public after school hours. Although this has been the case, it should be noted that the

former Karratha High School oval is not a formal Crown Reserve dedicated as public open space.

The primary public open space servicing the neighbourhood and locality is the Bulgarra Oval and

recreational facilties (i.e. Crown Reserve 32320 managed by the City of Karratha). The existing

Karratha Primary School oval is currently unfenced and this also is be used by the public after school

hours as open space. However, similar to the high school oval, it should be noted that the primary

school oval and grounds is not formally dedicated as public open space.

It is envisaged in the preparation and approval of a Structure Plan that the existing Karratha Primary

School would be retained on a site approximately 4.17 hectares. The proposed primary school site

area is consistent with WAPC DC Policy 2.4 School Sites, which prescribes a minimum public primary

school site area of 4.0 hectares. In addition, a sufficient area has been set aside for the Family Centre,

including the existing carpark being used by the Centre.

City of Karratha


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5.0 SUBDIVISION CONCEPT PLAN

A Subdivision Concept Plan (SCP) (Appendix 3) has been prepared as part of this report to show

potential future redevelopment of the subject site, whilst retaining the primary school and family centre

either on individual sites or within a balance reserve.

The Urban Development zone requires the preparation and approval of a Structure Plan, which would

identify future land uses and spatial layout of land uses. The Structure Plan could be prepared based

on the SCP baseline proposal. The subdivision concept plan generally provides for:

- The existing high school buildings and infrastructure to be demolished and the site remediated for residential development.

- The high school buildings are considered dated and would require substantial upgrades and maintenance for the buildings to be readapted for a sequential land use (i.e. offices or

commercial). Preliminary investigations of the existing high school buildings indicates that

upgrading the existing school building/s to the required Australian Standards for alternative

commercial use would be cost prohibitive. However, a Structure Plan could provide flexibility

for alternative sequential land use of the high school buildings, to retain such options for any a

prospective purchaser;

- A new north - south road (i.e. minimum 20m road reserve) to provide permeability and access to the primary school, which would include school bus embayments on the western side of the

school for pupil drop-off and pick-ups. The exact width of this road would be determined in

consultation with the Department of Education at the detailed subdivision design stage and

subject to feature survey;

- The existing primary school northern car park being retained within the proposed primary school site. The primary school northern lot boundary has been located to provide opportunity

to retain the existing carpark and for potential future expansion of the carpark. Expansion

plans could include provision of a new row of car bays on the northern side of the existing

primary school car parking access road. The lot boundary also provides adequate area for a

1.0m landscaping strip along the northern boundary of the primary school site, to provide a

vegetation buffer between residential lots and the school site. The exact subdivision boundary

would be determined by Department of Education at the detailed subdivision stage and subject

to feature survey;

- The existing primary school southern car park is retained within the proposed primary school site, with access to the new north-south spinal road and Turner Way;

- It is noted that existing dwellings in McKenzie Way, Hooley Street, Hall Street and Shakespeare Street (on the western side of Reserve 32335) are not orientated towards the drainage swale.

Dwellings are orientated north-south and side onto Reserve 32335. There is no significant

amenity for dwellings to orientate towards the drainage swale (Reserve 32335). As such,

proposed Lots 1, 8, 15, 31, 32 & 47 within the SCP are orientated to face and provide a

positive contribution to the residential streetscape, rather than orientate towards the drainage

swale.

City of Karratha


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- Orientating proposed Lots 1, 8, 15, 31, 32 & 47 will also provide for a more efficient development design (i.e. reduce development costs) by not having to provide a full width road

reserve and infrastructure along the western boundary of the subject site to provide for lots to be

orientated towards the drainage swale;

- Two 6m wide slip roads are provided along the western boundary of the site for vehicular permeability, access and for waste service vehicles;

- The existing fence at the northern end of the oval provides an indicative demarcation for provision of an interface strip between future development and Searipple Road reserve. No lots

are proposed with frontage to Searipple Road to avoid development costs (i.e. fill) to bring lots

up to a desirable servicing level with the road;

- The existing power infrastructure (compound) is retained on proposed Lot 49, which could be set aside as a Utility Reserve;

- The existing child health care centre is proposed to be retained on a separate lot with direct access to Searipple Road. The proposed lot could be set aside as a reserve for community

purpose. This site could be redeveloped for strata units if the centre is no longer required and

is demolished/relocated;

- The primary school site, utility site and family centre site could be identified as Public Purpose reservations under a Structure Plan, with the balance high school land identified as Residential

zone (i.e. a density code of R30);

- The open drain to the west could provide opportunity for urban stormwater drainage for the subject site subdivision and development; and

- There is opportunity for a proposed future road link between Turner Way and Emma Street as envisaged under the Karratha Revitalisation Strategy. This can be investigated at the structure

planning stage.

City of Karratha


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6.0 INFRASTRUCTURE & SERVICING

A Preliminary Engineering Servicing Report (Appendix 2) has been undertaken for the subject site. The

subject site is surrounded by existing urban development and would be considered an urban infill

development site, as opposed to a greenfield development site, which is usually found on the urban

fringe and which requires major extension of services and infrastructure.

In this instance, all major services run past the subject land and the subject site can be adequately and

readily connected to major service infrastructure subject to the necessary extensions and upgrades.

6.1 WASTEWATER

There is an existing large deep gravity reticulated sewer main within Searipple Road, which discharges

to the pumping station on the opposite side of Searipple Road. Existing reticulated gravity sewer mains

also exist within Turner Way and surrounding residential streets. Preliminary advice from Water

Corporation indicates future urban development of the subject site could be readily connected to

existing infrastructure.

6.2 WATER SUPPLY

Preliminary investigations indicate that there are existing reticulated water mains within the immediate

and surrounding streets, including Turner Way and Searipple Road. These water mains have capacity

to supply reticulated water to the proposed development within the subject site. Extensions would be

required to service future development within the subject site. Further consultation will be required with

Water Corporation as to the design requirements for future reticulated water supply infrastructure.

6.3 POWER

Preliminary desktop analysis indicates that there is sufficient capacity in the existing grid for development

of the subject site as proposed in the scheme amendment. There is an existing power sub-station in the

central northern portion of the subject site, which would likely be retained.

6.4 TELECOMMUNICATIONS

The subject site can be serviced by the existing telecommunications infrastructure within Searipple Road

and Turner Way. There is also existing optic fibre running through the subject site.

6.5 GAS

There is no reticulated gas network in Karratha.

City of Karratha


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6.6 SITE WORKS

Although the subject land is generally flat with gentle localised grades from north to south across the

site, earthworks to an extent is expected to create roads and level lots for dwelling construction,

adequate drainage for treatment, storage and disposal of stormwater and provision of services.

Siteworks will generally comprise of clearing the land, removal of unwanted materials (following

demolition of the high school buildings and infrastructure) and possibly some minor localised cut to fill.

As previously mentioned under section 2.8 Flooding, some areas of the northern portion of the site

maybe affected by 2110 flood mapping. It is likely that some filling within the northern portion of the

subject site will be required to accommodate future urban development. Retaining walls are likely to be

required to account for final finished filling and lot levels across the site, with all proposed residential

lots having a finished floor level 500mm above the 100 year flood level. This will be further

investigated as part of structure planning and subdivision design.

6.7 ROADS

Access to the subject site is currently from Searipple Road and Turner Way. The SCP proposes access

from these roads, with the proposal of a main north-south spinal internal road to service future

residential development and the existing primary school.

Proposed local roads can be considered as part of the structure planning and subdivision stage. Any

potential upgrades to existing roads can also be considered at the structure planning and subdivision

stage, along with any other potential external linkages with the surrounding road network.

6.8 STORMWATER DRAINAGE

There are two relatively wide drainage swales on both the western and eastern side of the subject site.

Preliminary stormwater drainage investigations indicate that the majority of stormwater generated from

the proposed urban development of the subject site (based on the SCP) could be directed into the

western drainage swale. Stormwater would potentially be directed towards the western drainage swale

via overland flow within the proposed road reserves.

City of Karratha


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7.0 CONCLUSION

The former Karratha High School on the subject site is a redundant Western Australian Department of

Education asset and has been closed. Pupils have been relocated to the new Department of Education

public high school, which has been developed at the Karratha College Campus site.

This report presents a proposal to initiate a Local Scheme Amendment to the City of Karratha Town

Planning Scheme No. 8 (TPS 8). The proposal seeks to reclassify Lot 4615 (Reserve 30602) Searipple

Road, Bulgarra from Public Purposes - Education local scheme reservation to Urban Development

zone.

The whole Lot 4615 (subject site) being reclassified to Urban Development as a Structure Plan can

identify the balance area containing the existing Primary School and Family Centre as Public Purpose.

The final balance area and lot boundaries would be determined subject to structure planning, feature

survey and detailed subdivision design.

The reclassification to Urban Development will provide opportunity to redevelop the site for a suitable

sequential land use, subject to the preparation and approval of a Structure Plan pursuant to Planning and

Development (Local Planning Schemes) Regulations 2015 Schedule 2 - Deemed provisions for local

planning schemes Part 4 Structure Plans.

This local scheme amendment report outlines the proposal and demonstrates that the site can be

adequately planned, serviced and developed for future urban development.

City of Karratha


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PLANNING & DEVELOPMENT ACT 2005

CITY OF KARRATHA

DISTRICT TOWN PLANNING SCHEME NO. 8

AMENDMENT NO. xxx

RESOLVED that the Council, in pursuance of Section 75 of the Planning and Development Act 2005, amend the

above local planning scheme by:

1. Reclassification of Lot 4615 (Reserve 30602) Searipple Road, Bulgarra from Public Purposes -

Education local scheme reservation to Urban Development zone and amending the Scheme Map

accordingly.

City of Karratha


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SCHEME AMENDMENT MAP

City of Karratha


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FIGURES

(Source: Google Maps, 2015 - modified)

FIGURE 1

LOCATION PLAN

(Source: Landgate - modified, 2014)

FIGURE 2

CADASTRAL/AERIAL PLAN

(Source: Landgate, 2015 - modified)

FIGURE 3

SURROUNDING CONTEXT

City of Karratha


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APPENDIX 1

CERTIFICATES OF TITLE

LANDGATE COPY OF ORIGINAL NOT TO SCALE

www.landgate.wa.gov.au

JOB 50136715Mon Feb 15 10:29:32 2016

City of Karratha


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APPENDIX 2

SERVICING REPORT

Job No: 15-009

Karratha High School Subdivision

for

Whelans

Revision Description Date

0 Issued for Review 13/02/2015

1

15-009 Karratha High School Subdivision Page i

Table of Contents

Table of Contents i

1 Introduction 2

2 Site Conditions 2

2.1 Geology 2

2.2 Topography 2

2.3 Groundwater Atlas 2

2.4 Acid Sulphate Soils (ASS) 2

2.5 Earthworks 2

3 Infrastructure 3

3.1 Roads 3

3.2 Stormwater Drainage 3

3.3 Sewerage Reticulation 3

3.4 Water Reticulation 4

3.5 Electrical Supply 4

3.6 Communications 4

3.7 Gas 4

4 Conclusion 5

Appendices

Appendix One: Subdivision Concept Plan

Appendix Two: Environmental Geology Series Maps

Appendix Three: 100 Year Flood Mapping

Appendix Four: Preliminary Earthworks Levels

Appendix Five: City of Karratha Review of Concept Plan

Appendix Six: City of Karratha Stormwater Design Guidelines for Residential Developments

Appendix Seven: Existing Water Corporation Sewer Infrastructure

Appendix Eight: Existing Water Corporation Water Infrastructure

Appendix Nine: Horizon Power Dial-Before-You-Dig

Appendix Ten: Existing Communication Infrastructure

15-000 Karratha High School Subdivision Page 2

1 Introduction

Pritchard Francis has been engaged by Whelans to undertake an Engineering Services Report for a proposed

subdivision on the existing Karratha High School (KHS) site.

This report outlines existing site conditions, adjacent services and likely development constraints. This report is based

on the subdivision concept plan contained within Appendix One.

2 Site Conditions

The site covers approximately 4.5ha in area and has frontages to an existing open drain to the west, Searipple Road to

the north, Turner Way to the south and Karratha Primary School to the southeast.

The site currently contains the Karratha High School which is to be demolished.

2.1 Geology

The Dampier sheet of the 1:250,000 scale Environmental Geology series maps, Appendix Two, indicates the site as

having soil profiles as follows:

Sand, silt, and clay in distal outwash fans, with gilgai surface in areas of expansive clays.

A detailed geotechnical investigation would need to be done to confirm the soil profile.

2.2 Topography

Water Corporation contours for the site indicate that it grades from approximately 9m AHD in the south to 6m AHD

adjacent to Searipple Road.

2.3 Groundwater Atlas

No historical groundwater data exists for the site but considering the sites close proximity to the coast there is

potential for a high groundwater table. The groundwater levels will need to be confirmed via geotechnical investigation

and/or monitoring bores.

2.4 Acid Sulphate Soils (ASS)

Department of Environment Regulations ASS mapping indicates that the site has a low risk of ASS and PASS. Due to

its proximity to areas in Karratha which do have high risk of ASS and PASS it is recommended an ASS investigation is

undertaken on the site.

2.5 Earthworks

The site currently grades from south to north with approximately 3m of fall across the site. It is expected that based on

other sites in Karratha the site will contain reactive soils however the level of reactiveness would need to be confirmed

via a geotechnical investigation.


JDA Consultant Hydrologists undertook a coastal vulnerability study in August 2012. As part of this study they

modelled 100 year flood levels for the 2010 climate and predicted 2060 and 2110 climates. The flood levels on the

northern side of Searipple Road for 2010, 2060 and 2110 are 5.5m AHD, 5.6m AHD and 5.8m AHD respectively, refer

Appendix Three for 100 year flood mapping. The 2110 flood map shows some flooding of the northern area of the site.

It is advised that a review is done of the drainage modelling for the site to confirm flood levels but at this stage it could

be assumed the northern portion of the site will need fill. Retaining walls will be required to account for the fall across

the site. All lots will need to have finsished floor levels 500mm above 100year flood levels

Refer Appendix Four for preliminary earthwork levels

3 Infrastructure

3.1 Roads

The main access to the site will be from Searipple Road to the north. A detailed intersection analysis will be required

for this intersection in order for it to cater for expected traffic volumes.

Secondary access will be via Turner Way to the south.

The City if Karratha have undertaken a preliminary review of the development plan and have queried how access will

be maintained for the Child Health Care site, refer Appendix Five.

3.2 Stormwater Drainage

There are two large swales on the west of the site and on the east of the site. Based on preliminary comments from the

City of Karratha the majority of the site will be drained into the western swale. The City of Karrathas Stormwater

Design Guidelines For Residential Developments, refer Appendix Six, states that post development flows should not

exceed pre-development flows.

It is possible that some compensation areas will be required but considering the relatively small area of the

development, the current semi-developed nature of the site and the fact the site is at the downstream end of the overall

catchment, it is likely the City will allow water to be flow directly into the adjacent swales without compensation.

Stormwater flows will be directed towards the main drainage system via overland flow within the road reserves.

It is likely lots 48-62 will drain directly towards Searipple Road.

3.3 Sewerage Reticulation

There is existing deep gravity sewer on the northern side of Searipple Road which discharges into a pump station

opposite the northeast corner of the site. There is also an existing 430mm pressure main on the western boundary of the

site which will need to be protected throughout construction. It is expected there is capacity in this existing gravity

system to accept sewer from the site. A planning request has been submitted to the Water Corporation but no response

had been received at the time of publishing of this report.


Existing Water Corporation Sewer Infrastructure can be found in Appendix Seven.

3.4 Water Reticulation

The site currently has 150mm asbestos water mains on its northern, western and southern boundaries in Searipple

Road, McKenzie Way and Turner Way respectively. It is likely that connections into the mains in Searipple Road and

Turner Way will be able to supply the site with water. A planning request has been submitted to the Water Corporation

but no response had been received at the time of publishing of this report.

Existing Water Corporation Water Infrastructure can be found in Appendix Eight.

3.5 Electrical Supply

Existing electrical infrastructure adjacent to the site includes:

High and low voltage underground cables in Searipple Road.

High voltage cable on the western boundary of the site.

High voltage and low voltage cable on Turner Way.

Substation in north of site.

Substation in south of site.

Low voltage underground cables within the site.

It is likely the existing network will have spare capacity to service the site. Refer Appendix Nine for Horizon Power

Dial-Before-You-Dig information.

3.6 Communications

There is existing Telstra copper network located in Searipple Road and Turner Way as well as within the site. There is

also existing optic fibre running through the site. The Telstra infrastructure within the site would need to be realigned

to suit the proposed road layout. It is expected that there will be capacity in the system to service the site.

It would need to be confirmed with NBN Co as to whether they would service this development. However, as it is less

than 100 lots they may choose not to. If this is the case then Telstra would service the development. Regardless of

which authority services the development, the developer will be required to install pit and pipe at their expense. Refer

to Appendix Ten for Existing Communication Infrastructure.

3.7 Gas

There is no reticulated gas network in Karratha.


4 Conclusion

The development of the Karratha High School Site would not appear to be constrained by service capacities or

upgrades with all services in close proximity to the site.

It is expected that existing sewer and water networks will have capacity however formal advice is yet to be received

from the Water Corporation.

There is an existing low and high voltage power network adjacent to the site as well as existing infrastructure within

the site.

Communications infrastructure within the site will need to be realigned to suit proposed road reserves.

Imported fill will likely be required in the north of the site to ensure finished lot levels are above 100 year flood levels.

Onsite stormwater compensation will also likely be required following consultation with the City of Karratha


Appendices











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5.25.8

6.16.3

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6.96.56.36.3

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6.26.1

5.9

5.9

5.85.8

7.96.6

5.49.3

7.46.2

5.35.2

5.75.2 5.25.2 4.9

5.5

5.14.7

5.95.95.95.96.6 6.5 6.5 6.5 6.4 6.4 6.3 6.3 6.2 6.2 6.2 6.2

6.16.1

6.1 6.16.1

6.1 5.9 5.95.9

6.16.16.16.16.2

6.26.26.26.26.2

6.26.2

6.36.46.46.46.46.46.56.56.66.76.86.86.86.96.9

6.16.16.16.36.46.46.36.36.3

6.36.36.36.35.6

6.25.66.3

6.46.56.76.56.1

6.36.56.5

5.86.46.66.66.8

6.86.96.76.86.86.86.8

6.76.6 6.5 6.3

6.5 6.36.46.5

6.86.6

6.6

7.4

18.7 14.1 10.3

31.1 29.5

29.328.731.8

28.132.936.4

26.2

25.9 24.123.1 21.1

36.2

26.9

31.1

25.2 23.323.4 21.320.1

18.8

24.4

29.3

19.918.2

16.5

13.1

14.613.114.816.5

18.3 16.6

20.624.4

15.3

21.619.9

17.7

15.614.7

13.411.9

10.7

Tag Points(WaterLevel)(m AHD)#*

100yr Flood Extent0.5m Contour (m AHD)Cadastre

Job No. J4812

COPYRIGHT JIM DAVIES & ASSOCIATES PTY. LTD. 20110 0.5 1 1.5 2KilometersScale:1:22,000 LandCorpKarratha Coastal Vulnerability Study :Main ReportFigure 12B: 100yr ARI Flood Elevation - 2010 Climate Scenario - Sheet B

FEDBA CKarratha

NickolBay

1:500,000

Map Index

Note: No Water Levels are shownwithin town creeks due to model grid limitations

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6.86.25.7

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5.65.85.3 5.3

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4.8

6.26.26.26.26.26.36.36.36.9 6.9 6.9 6.8 6.8 6.7 6.7 6.6 6.6 6.5 6.5 6.56.4

6.46.4 6.4

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6.36.36.46.46.46.46.5

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6.56.5

6.66.76.86.76.76.86.86.96.97.17.17.17.2

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7.37.1 7.3 6.8

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18.3

16.5

13.1

14.8

18.3

24.5

21.8

17.917.215.8

14.813.512.1

10.8



Job No. J4812


FEDBA CKarratha

NickolBay

1:500,000

Map Index


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5.55.5

6.66.76.76.76.76.76.86.87.3 7.3 7.2 7.2 7.2 7.1 7.1 6.9 6.9 6.96.9

6.86.8 6.8

6.86.8 6.7 6.8 6.7 6.7

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6.86.86.86.86.96.96.9

6.96.96.96.9

7.17.27.37.37.37.47.57.57.57.57.5

6.96.96.96.97.16.96.9

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6.87.17.2

7.17.17.27.26.5

7.27.37.57.4

7.47.57.5 7.57.67.47.57.57.57.57.6

7.9 7.7 7.67.5 7.4

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8.18.2

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17.6 10.912.1

18.8 16.8 14.1

12.1

10.3

35.8 31.3 29.6

29.428.831.8

26.928.232.936.4

26.2 25.1

26.1 24.323.2 21.2

36.2

26.9

31.2

25.2 23.323.4 21.420.2

18.918.1

24.5

29.3

25.1

18.3

16.6

13.1

16.414.613.214.916.6

18.3 16.7

20.724.5

22.7

15.4

21.8

17.315.9

14.913.612.2

10.8



Job No. J4812


FEDBA CKarratha

NickolBay

1:500,000

Map Index


To link this development with the dual use path 2.5m wide already in place on McKenzie and continue along Searipple road

Stormwater outlets with rock protection for the drains

Stormwater outlets with rock protection for the drains

Footpaths to be on property boundary line and not back of kerb

What happened to access road for the Child Health Care.

Stormwater Design Guidelines for

Residential Developments

June 2011

Stormwater Design Guidelines June 2011 Residential Developments

Contents

1 Introduction 3 1.1 General 3 1.2 Background 3 1.3 Developer Responsibilities 3 1.4 Development within Drainage Reserves 4 1.5 Water Sensitive Urban Design (WSUD) 4 1.6 Innovation 5 1.7 Other texts 5

2 Design Parameters for Small Developments 6 2.1 General 6 2.2 Flood Events 6

3 Design Parameters for Large Developments 7 3.1 General 7 3.2 Flood Events 7 3.3 Maintenance 8

4 Vegetation 9 4.1 General 9

Table Index

Table 1 Design Storm Events 4 Table 2 Recommended species for establishment in new drainage reserves 9


1 Introduction

1.1 General This document has been prepared to assist developers meet the expectations of the Shire of Roebourne

(the Shire) in drainage of any development in a residential area.

The Shire is the authority responsible for the future care, control and management of the road and

stormwater drainage infrastructure. All designs submitted will be checked against these guidelines and

the Shire reserves the right to request revisions or further details if they are not satisfied with the

information supplied.

1.2 Background Typically the drainage network in the developed areas of the Shire operate by capturing flows within

developed residential area and conveying the water to topographic low points and discharging through

open drainage channels. The channels vary in size and shape, depending on the volumes of water they

convey.

The current drainage network within the Shire has proven to be an effective system that performs its

function well. Any proposed modifications will undergo close scrutiny as it may impact on the hydraulic

capacities of drainage control points such as road crossings. It is important that new developments are

designed to ensure post development flows do not exceed pre development flows so additional pressures

are not placed on these drainage points within the network.

1.3 Developer Responsibilities Any developer subdividing or developing land for residential purposes is required to undertake

stormwater drainage design. Although the extent of the design will vary in accordance with the size of the

development, in a basic context it will involve examination of the total drainage catchment area to ensure

any upstream drainage may pass through the development is included in the design and the drainage

system developed is capable of carrying the ultimate design flow from the upstream catchment as well as

the developed land. The drainage system shall be designed to cater for two different storm events:

1. The initial storm

2. The major storm

1.3.1 Shared Drainage Systems Developers whose land shares a common drainage catchment have a responsibility for ensuring that the

whole of the catchment, including major roads are drained.

Larger developments which may have a staged development process will be required to demonstrate an

overall drainage plan for the entire catchment prior to obtaining approval for any individual stages.

1.3.2 Existing Drainage Systems If, during the design phase it is determined that existing drains do not meet the requirements of the new

development then the developer must arrange appropriate approvals for altering the existing

infrastructure prior to undertaking any works. Under no circumstances will any alteration to existing drain

be permitted without authorisation.

1.3.3 Outfall to Private Property In instances where stormwater is to be discharged into private land downstream of a development, the

developer must ensure that an easement is provided over the route of the drain in addition to constructing

and/or improving the drainage outlet. The easement shall be in favour of the Shire of Roebourne


1.3.4 Preliminary Drainage Proposal A preliminary drainage proposal and investigation will be required which defines the drainage

requirements for initial and major storms, identifies types and location for Water Sensitive Urban Design

(WSUD) strategies, considers upstream and downstream catchments, identified necessary floodways

and any upgrades required to existing infrastructure. Results of this investigation shall be included on a

masterplan for drainage which shall be provided to the Shire for approval prior to commencing any

development.

1.3.5 General Design Parameters The developer in consultation with the drainage designer will be responsible for determining suitable

runoff coefficients and characteristics for a drainage system based on the ultimate development of all

allotments for the relevant land zoning. Storm events shall be in accordance with table 1 below

Table 1 Design Storm Events

Catchment Zoning Initial Storm Major Storm

All open spaces 2 year 100 year

All other Zones 5 Year 100 year

1.4 Development within Drainage Reserves Any proposed development that impinges on drainage reserves will require detailed investigation. The

Local Government Guidelines for Subdivision Development 2009 Edition 2 (IPWEA 2009) illustrate a

floodplain development strategy and identify a flood fringe that can be utilised if necessary. The minimum

requirement for this type of impingement will include a hydrologic and hydraulic assessment to

demonstrate:

Minimum habitable floor level of 0.5 m above the 100 year ARI flood level.

Total development within the flood fringe does not raise the 100 year ARI flood level by more than

0.15 m

Environmental considerations are also major design requirements for all drainage infrastructure and

subdivision designs must be undertaken in consultation with relevant agencies. In particular, soil erosion

and sediment control will be necessary both during construction and maintenance periods.

To avoid mosquito breeding and associated issues, all drainage systems and associate structures should

be designed in consultation with the Department of Health.

1.5 Water Sensitive Urban Design (WSUD) The Shire supports the principles of WSUD and recommends they be adopted to suit the climatic and

ground condition of the region. All developers are to maintain surface and groundwater quality at pre-

development levels (winter concentrations) and improve the quality of water leaving the developed area,

if possible. All runoff contained in the drainage infrastructure network needs to receive treatment prior to

discharge into the environment consistent with the Stormwater management manual (DoW, 2004-2007). The following elements can be considered as part of the design:

Combining drainage reserves and recreation reserves with appropriate landscaping. This should include

an assessment of irrigation water demands to determine whether the water supply network has adequate

capacity. Landscaping should not impact on the hydraulic function of the drainage system.

WSUD at the source of stormwater generation by encouraging landscaping to reduce peak flows to open

drains.


Use of v-notched weirs or drop structures within open drains to provide detention and treatment of low

flows with the aim of reducing flow velocities to limit erosion and reduce downstream sedimentation.

1.6 Innovation The Shire supports innovation in stormwater design, however good supportive evidence must be supplied

with any proposal.

1.7 Other texts The Shire acknowledges that the Local Government Guidelines for Subdivisional Development by the

Institute of Public Works Engineers Australia (Guidelines for Subdivision) are considered as the minimum

standard for subdivision development and are to be read in conjunction with this document and other

policies and legislations relevant to Agencies associated with subdivisional approvals.

Better Urban Water Management (WAPC 2008) was developed to facilitate better urban water

management of our urban water resources by ensuring an appropriate level of consideration is given to

the total water cycle at each stage of the planning system and should also be considered in association

with Local Government Guidelines for Subdivisional Development during the development process within

the Shire.


2 Design Parameters for Small Developments

2.1 General Small developments are classed as developments on less than five lots. This includes any development

of enhancement of a pre-existing developed lot. Typically they will not incorporate any provision for public

roads or servicing and stormwater disposal requirements will be local in nature.

In general the drainage system and all associated structures should be designed as follows:

Maximum flow velocities in open channels shall not exceed 2 m/s in open channels without suitable

erosion protection (can be arrested by the inclusion of drop structures);

Mortared stone pitching shall be provided in open drains at all outlet structures, junctions and bends

greater than 22.5o

Detention storage areas may be provided at suitable locations (can be in line) to reduce peak flow

rates to the capacity of downstream facilities

The minimum habitable floor level shall be 500 mm above the 100 year ARI flood level.

Drainage channels should be constructed with minimum 1:4 side slopes and vegetated where

possible to limit erosion of drain sides

Appropriate safety measures shall be provided to protect the public from being trapped within a drain

during flash flooding

2.2 Flood Events Storm recurrence intervals for the two defined storm events shall be in accordance with the following:

2.2.1 Minor Events The roof of any building shall not contain downpipes and will discharge directly to the lot.

Lots should be landscaped to prevent direct runoff from impervious surfaces to the drainage network

(roads or arterial drains) and to prevent erosion.

Open drains provided as part of the development will be designed to convey the 5 yr ARI event flows,

2.2.2 Major Events Any additional capacity within drainage reserves will be designed to convey 100 yr ARI flows


3 Design Parameters for Large Developments

3.1 General Large developments are classed as developments of five lots or greater and will typically include public

services like roads, parks and utilities. Stormwater disposal requirements will primarily be catchment

focussed.

The ideal drainage network in this case is represented by utilising kerbed roads as the initial conveyor of

stormwater, with kerb breaks located at topographic low points discharging to large open channels that

direct the stormwater away from the urban zone.

In general the drainage system and all associated structures should be designed as follows:

The top water level for the design of open channels shall be greater than 300 mm below the level of

the road shoulder for the 5-year ARI event

Maximum flow velocities in open channels shall not exceed 2 m/s in open channels (can be arrested

by the inclusion of drop structures)

Mortared stone pitching shall be provided in open drains at all outlet structures, junctions and bends

greater than 22.5o

Detention storage areas may be provided at suitable locations to reduce peak flow rates to the

capacity of downstream facilities

The minimum habitable floor level shall be 500 mm above the 100 year ARI flood level

Drainage channels should be constructed with minimum 1:4 side slopes and vegetated where

possible to limit erosion of drain sides

3.2 Flood Events Flood events should be catered for as follows:

3.2.1 Minor Events The roof of any building shall not contain downpipes and will discharge directly to the lot.

Lots should be landscaped to prevent direct runoff from impervious surfaces to the drainage network

(roads or arterial drains) and to prevent erosion.

The road network will be used as the primary conveyor of stormwater, designed with kerbs to contain all

flows within the 5 Yr ARI event.

Kerb breaks will be provided at appropriate low points throughout the road network to discharge

stormwater to drainage reserves and vegetated open channels in a controlled manner.

The main channel in open drains will be designed to contain the 5 year ARI event and where appropriate

Water Sensitive Urban Design (WSUD) principles in the form of sedimentation basins, gabions, V notch

weir structures incorporated to maintain low flow velocities and allow settling of suspended solids

Mortared stone pitching or other suitable scour protection shall be provided in open drains at all outlet

structures kerb breaks, kerb returns, open drain junctions and bends greater than 22.5o


3.2.2 Major Events Flow generated in excess of the 5 Yr ARI event will form overland flow paths by flooding of the road

reserve directing stormwater to drainage reserves.

The drainage reserves will be designed to contain all 100 yr ARI flows.

Developments will need to demonstrate that the 100-year flood level in downstream drainage reserves

does not increase by more than 0.15 m as a result of the development.

Weir structures or other drop structures shall be provided in arterial drains to limit downstream

sedimentation and ensure velocities do not exceed 2 m/s.

3.3 Maintenance The drainage system shall take into consideration requirements of future maintenance activities including

the provision for safe plant access for cleaning, silt removal and maintenance of vegetation.


4 Vegetation

4.1 General Maintaining a level of vegetation cover in constructed features such as drainage reserves is important for

increasing soil stabilisation and reducing erosion. Vegetation can act to inhibit stormwater flows and

potentially lead to flooding in serious cases; however a balance of vegetation cover is required to ensure

the optimal drainage system performance.

Drainage channels should be vegetated with native grasses whilst trees should occupy drainage

reserves. It is preferred that shrubs not be used in drainage reserves due to the additional maintenance

requirements. Species should be selected to reduce water requirements with watering to assist in

establishment and reduced to zero by handover. Table 2 below has examples of species that are

considered suitable however this is not an exhaustive list and other species approved by the Shire can be

considered

Table 2 Recommended species for establishment in new drainage reserves

Category Species Habitat

Trees

Eucalyptus victrix (Western Coolibah); 1 12 m

Floodplains and flats

Terminalia canescens (Joolal); 1 10 m

Variety of habitats

Grasses

Cymbopogan ambiguus (scent grass)

Variety of habitats

Themeda triandra Variety of habitats

BULGARRA

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BULGARRA

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The Water Corporation has taken due care in the preparation of this map but accepts no responsibilityfor any inaccuracies or inappropriate use. This plan may be reproduced in its entirety for the purposeof site work planning but shall not otherwise be altered or published in any form without the permissionof the Water Corporation. The Water Corporation may need to be advised of any planned grounddisturbing activities near facilities on this map. Refer to Brochure - "Protecting Buried Pipelines".Please report any inaccuracies to Spatial Information Management Group on (08) 9420 3496.of 6 Water

Information Brochure Damage43457587Print Date:

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