stormwater management strategy

Stormwater Management Strategy

Central Precinct North Lot 66 Ocean Drive, Bunbury

Draft A, July 2015

This report was prepared by:

Coterra Pty Ltd trading as COTERRA ENVIRONMENT ABN: 92 143 411 456 Our Ref: TPGCPN02 Author(s): C Hopkirk Reviewer: K. Chandler Report Version: Draft A Date: July 2015

This report was prepared for:

Home Art Building Group 11/63 Knutsford Ave, Riverdale WA 6103

Notice

This document is and shall remain the property of Coterra Environment. The document may only be used for the purposes for which it was commissioned. Unauthorised copying or use of this document is prohibited

TPGCPN01 – Draft A, July 2015 Page i

EXECUTIVE SUMMARY

This document outlines the Stormwater Management Strategy (SMS) for the site, which has been developed in accordance with the Better Urban Water Management (BUWM) guidelines (WAPC, 2008). The tables below provide an overview of the site and a summary of the design elements and requirements for best management practices and control points.

Site Overview Description

Site location Lot 66 Ocean Drive, Bunbury (Figure 1)

Size Approximately 0.28 ha

Planning context The site is currently zoned ‘Urban’ under the Greater Bunbury Region Scheme (GBRS) and ‘Special Use’ under the City of Bunbury Town Planning Scheme No. 7 (TPS7).

Proposed change in land use

The site is currently undeveloped and partially vegetated.

The structure plan prepared for the site proposes a mixed use development with residential and commercial lots and parking.

Hydrological constraints

High density development with mixed use

Soils are weak to moderately adsorbing of phosphorous

Hydrological opportunities

Highly permeable soils.

Ability to connect to existing stormwater network.

Proximity of ocean for discharge of extreme runoff events.

Large separation distance between existing topographic levels and maximum groundwater levels.

Key Elements Design and Compliance to Objectives

Stormwater Management (Section 3)

Runoff up to and including the 1 year ARI event will be fully retained and infiltrated onsite.

Onsite storage and infiltration will be achieved through a combination of rain-gardens and soakwells/underground storage areas.

The storage volumes proposed within the development are in line with the City of Bunbury’s minimum storage requirement (1 m3 per 65 m2 of impermeable surface).

Runoff above the 1 year ARI and up to and including the 100 year ARI event will overflow into the Ocean Drive existing drainage network. Discharge to the Ocean Drive road drainage system will be restricted to pre-development flow rates.

Water quality treatment of smaller events (‘first flush’) from carparks will be provided through the use of raingardens.

Gross pollutant traps and non-structural controls (such as controlled landscaping and provision of litter bins) will also be used to manage water quality.

Infiltration areas will be designed so that there is no standing water for more than 96 consecutive hours to manage the risk of mosquitos.

TPGCPN01 – Draft A, July 2015 Page ii

Key Elements Design and Compliance to Objectives

Groundwater Management

The base of infiltration areas/infiltration devices will be a

minimum of 300 mm above maximum groundwater levels.

Finished lot levels will be a minimum of 1.2 m above maximum groundwater levels

TPGCPN01 – Draft A, July 2015 Page iii

TABLE OF CONTENTS Page

1.0 INTRODUCTION ............................................................................................................. 1

1.1 Planning Context ......................................................................................................... 1

1.2 Guidance and Previous Studies ................................................................................... 1

1.3 Objectives ..................................................................................................................... 2

2.0 SITE CHARACTERISTICS ........................................................................................... 3

2.1 Previous and Existing Land Uses ................................................................................ 3

2.2 Climate and Rainfall..................................................................................................... 3

2.3 Topography .................................................................................................................. 3

2.4 Geology and Soils ........................................................................................................ 3

Regional Soil Description ............................................................................. 3 2.4.1

Phosphorus Retention Index (PRI) ............................................................... 4 2.4.2

Acid Sulphate Soils ........................................................................................ 4 2.4.3

2.5 Groundwater ................................................................................................................ 5

Groundwater Levels ...................................................................................... 5 2.5.1

Groundwater Quality ..................................................................................... 5 2.5.2

Public Drinking Water Supply ....................................................................... 6 2.5.3

Contaminated Sites ....................................................................................... 6 2.5.4

2.6 Vegetation .................................................................................................................... 6

3.0 STORMWATER MANAGEMENT .............................................................................. 7

3.1 Existing Drainage ......................................................................................................... 7

3.2 Proposed Drainage Strategy Overview ....................................................................... 7

Drainage Objectives and Targets ................................................................. 7 3.2.1

Drainage Overview ........................................................................................ 8 3.2.2

3.3 Catchment Areas.......................................................................................................... 8

3.4 Stormwater Events ....................................................................................................... 9

1 Year ARI Event ............................................................................................ 9 3.4.1

5 Year ARI Event and above ......................................................................... 9 3.4.2

3.5 Storage Sizing and Flow Rates .................................................................................... 9

Storage Areas .............................................................................................. 10 3.5.1

3.6 Water Quality Treatment ........................................................................................... 11

TPGCPN01 – Draft A, July 2015 Page iv

Gross Pollutant Traps ................................................................................. 11 3.6.1

Vegetation ................................................................................................... 11 3.6.2

Soil Amendment .......................................................................................... 11 3.6.3

Non-Structural Controls .............................................................................. 11 3.6.4

3.7 Public Open Space ..................................................................................................... 11

4.0 GROUNDWATER MANAGEMENT ....................................................................... 12

4.1 Proposed Earthworks ................................................................................................. 12

Separation Distances .................................................................................. 12 4.1.1

5.0 IMPLEMENTATION ..................................................................................................... 14

6.0 REFERENCES .................................................................................................................. 15

TPGCPN01 – Draft A, July 2015 Page v

TABLES (Compiled within the report) Page

Table 1 Design Objectives and Criteria .................................................................... 2

Table 2 Rainfall Average Monthly Statistics.............................................................. 3

Table 3 Relative permeability and PRI for various substrates ................................. 4

Table 4 PRI Fixation Properties .................................................................................. 4

Table 5 Regional Peak Groundwater Levels .............................................................. 5

Table 6 Regional Water Quality Data ........................................................................ 5

Table 7 Pre and Post Development Flows ............................................................... 10

Table 8 Storage Requirements ................................................................................ 10

Table 9 Storage Areas .............................................................................................. 10

Table 10 Roles and Responsibilities for Implementation ....................................... 14

FIGURES (Compiled at the end of the report)

Figure 1 Site Location

Figure 2 Topography and Geology

Figure 3 Groundwater

Figure 4 Catchment Areas

APPENDICES

Appendix A Development Concept Plans

Appendix B Engineering Design Synopsis and Calculations

TPGCPN01 – Draft A, July 2015 Page 1

1.0 INTRODUCTION

Lot 66 Ocean Drive, Bunbury (‘the site‘) is located in the City of Bunbury, approximately 180 km south of Perth (Figure 1). It is set back approximately 50 m from the beach and is situated to the south-west of Bunbury Senior High School. The site is bound by Lot 76 to the north, Ocean Drive to the west, Scott Street to the south and Upper Esplanade to the east (Figure 1), occupying an area of approximately 0.28 ha.

This Stormwater Management Strategy (SMS) has been prepared on behalf of The Planning Group (TPG) and relates to the proposed development of the site.

1.1 Planning Context

Lot 66 is currently zoned ‘Urban’ under the Greater Bunbury Region Scheme (GBRS) and ‘Special Use’ under the City of Bunbury Town Planning Scheme No. 7 (TPS7). To facilitate future development of the Back Beach Tourism Mixed Use Precinct (TPS Amendment No. 66), the Back Beach Tourism General Structure Plan (City of Bunbury, 2015) was released in April 2015.

A development concept plan has been prepared by TPG for the site. The concept plan indicates that the site will contain commercial space and high density residential accommodation. The concept plans for each level within the development is provided in Appendix A.

1.2 Guidance and Previous Studies

A Local Water Management Strategy (LWMS) is usually required at Local Structure Planning (LSP) stage to support rezoning under a Town Planning Scheme (WAPC, 2008). However, in some instances a LWMS may not be required or the scope may be reduced. City of Bunbury (CoB) has advised (based on advice from Department of Planning and Department of Water) that a LWMS is not required for Lot 66 and that a Stormwater Management Strategy (SMS) is sufficient. Further liaison with CoB identified the objectives and scope of the SMS. These are as follows;

Outline the high level guiding principles and objectives for stormwater

management on site. These principles should be consistent with the CoB

information guides provided where possible.

Briefly outline the proposed stormwater management system and storage

requirements to demonstrate that sufficient space has been set aside for

stormwater management.

Briefly outline the proposed stormwater quality treatment measures.

Briefly describe the proposed public open space areas, and indicate the

irrigation water requirements and source.

Describe groundwater levels at the site and any proposed management

measures.


During liaison, CoB also outlined their engineering requirements for the stormwater design. These requirements are detailed further in Section 3.2. In addition to CoB advice, the following documents were considered in preparing this SMS:

Better Urban Water Management (WAPC, 2008).

Western Australian State Water Plan (Government of Western Australia, 2007).

Stormwater Management Manual for Western Australia (DoW, 2004-2007).

Local Government Guidelines for Subdivisional Development Edition 2.2

(Institute of Public Works Engineering Australia, 2012).

Water Monitoring Guidelines for Urban Water Management Strategies/ Plans

(DoW, 2012).

1.3 Objectives

In the absence of a District Water Management Strategy (DWMS), the design objectives and criteria for this site have been derived from the LWMS Design Objectives for Water Sensitive Urban Design (DoW, 2008). These are summarised in Table 1.

Table 1 Design Objectives and Criteria

Element Objective Design Criteria

Water quantity management

Manage post-development discharge volume and peak flow.

Events up to and including the 1 year ARI shall be fully retained and infiltrated on site.

Post development runoff rates shall not exceed pre-development runoff rates, up to and including the 100 year ARI event.

Water quality management

Maintain pre-development groundwater quality.

Ensure that road and car park runoff up to and including the 1 year ARI event (‘first flush’) receives water quality treatment prior to discharge to a receiving environment.

Reduce the health risk from mosquitoes.

Retention and detention treatments should be designed to ensure that detained immobile stormwater is fully infiltrated or discharged within a time period not exceeding 96 hours.


2.0 SITE CHARACTERISTICS

2.1 Previous and Existing Land Uses

The site is currently undeveloped with some vegetation. The site has previously been occupied by three residential dwellings (prior to 1996) that have since been removed.

Urban development occurs adjacent to the eastern boundary of the site. The lots to the north and south of the site are proposed urban development and form part of the Back Beach Tourism Precinct. There are no known surrounding land-uses which would require a buffer to the likely range of uses proposed by the scheme amendment.

2.2 Climate and Rainfall

The site has a Mediterranean climate, with hot, dry summers and mild, wet winters. The average annual rainfall at the site is approximately 724 mm. The monthly averages are presented in Table 2 (BOM, 2015).

Table 2 Rainfall Average Monthly Statistics

Month Average Rainfall (mm)

January 10.6

February 6.3

March 15.5

April 36.2

May 102.0

June 142.0

July 142.3

August 117.6

September 86.6

October 31.2

November 25.7

December 19.6 Source: Bureau of Meteorology. Bunbury weather station (Averages from 1995-2015)

2.3 Topography

The aspect of the site slopes towards the coast, with topography ranging from approximately 17 mAHD along the eastern boundary to approximately 11 mAHD on the western boundary (Figure 2).

2.4 Geology and Soils

Regional Soil Description 2.4.1

The site is part of the Quindalup landform which consists of dunes and beach ridges composed of calcareous sand (Churchward & McArthur, 1978). The geological sub-unit present on the site is Safety Bay Sand (Qhs) (Geological Survey of WA) (Figure 2).


Safety Bay Sand is defined as white, unlithified, calcareous fine to medium-grained quartz sand and shell fragments with traces of fine-grained, black, heavy minerals. It occurs along the coastal margin as stable and mobile aeolian dunes, which overlie the Tamala Limestone and Becher Sand (McPherson and Jones, no date). These sands are highly permeable and free draining.

Karst can be present in Tamala Limestone geological units. The potential for karst to occur onsite will be further reviewed during geotechnical investigations undertaken at the detailed design stage.

Phosphorus Retention Index (PRI) 2.4.2

In the absence of site specific testing, the Department of Environment (cited in DoW, 2004-2007) and Department of Agriculture and Food general guidelines have been used to provide an indication of Phosphorous Retention Index (PRI) of different soil types.

The properties of Safety Bay sands generally range between those of Bassendean Sands and Cottlesloe Sands. This suggests that the site soils would have a PRI of between 0 and 12, which is classified as ‘weakly to moderately adsorbing’ of phosphorous (Table 4).

Table 3 Relative permeability and PRI for various substrates

Substrate Permeability (m/day) PRI

Bassendean Sands 30+ 0-0.5

Karrakatta Sands 10+ 2-4

Cottesloe Sands 10+ 5-12

Crushed limestone or lime sands 2-5 5-20

Natural clay or loam soils <0.4 30-1,000+

Source: Department of Environment

Table 4 PRI Fixation Properties

PRI (mL/g) Description

Negative desorbing

0–2 weakly adsorbing

2–20 moderately adsorbing

20–100 strongly adsorbing

>100 very strongly adsorbing

Source: Department of Agriculture and Food

Acid Sulphate Soils 2.4.3

Acid Sulfate Soil (ASS) risk mapping (Landgate, 2015) for the site indicates that there is a ‘low to nil risk of acid or potentially acid sulphate soils occurring >3 m below the ground surface’ (WA Atlas, 2015).


2.5 Groundwater

Groundwater Levels 2.5.1

There are no regional groundwater contours in the vicinity of the site (DoW, 2015b), however there are a number of DoW WIN bores within a 1 km radius of the site.

The site is located approximately 50 m away from the coastline, and sea levels will have a controlling influence over peak groundwater levels at the site. The four bores with the longest record which are close to the site are presented in Figure 3. WIN Bore 1559 (61118026) is the closest bore to the ocean and therefore likely to be most representative for the site. A summary of the peak groundwater levels are presented in Table 5 (DoW, 2013c).

Table 5 Regional Peak Groundwater Levels

WIN Bore ID Location Distance to Coast

Peak Groundwater Level (mAHD)

20012429 (61110363)

1 km north east of site 560 m 1.52

1536 (61118003)

0.5 km north east of site 300 m 1.29

1558 (61118025)

1 km south west of the site 200 m 1.61

1559* (61118026)

1 km south west of the site 90 m 0.55

* Most representative of the site.

With peak groundwater levels at approximately 0.5 mAHD, this would provide approximately 10.5 to 16.5 m separation between the existing ground levels and peak groundwater levels.

Site specific groundwater monitoring has not been undertaken for the site given the significant separation to groundwater.

Groundwater Quality 2.5.2

Site specific groundwater monitoring has not been undertaken for the site. Given the close proximity of the site to the ocean, it is likely that the superficial aquifer underlying the site is brackish (1,000-1,500 mg/L) (DoW, 2013a).

The DoW WIN database (DoW, 2013c) provides some water quality data from surrounding regional bores. A summary of the relevant available water quality data is presented in Table 6.

Table 6 Regional Water Quality Data

ANZECC guidelines (Irrigation and General Water Use)

WIN Site ID 1536

(61118003) 1558

(61118025) 1559

(61118026) pH 6.0 - 8.5 - 6.4 -

Cl (sol) (mg/L)

<175 (sensitive crops) 175 – 350 (moderately sensitive crops) 350 – 700 (moderately tolerant crops)

>700 (tolerant crops)

618 268 99


ANZECC guidelines (Irrigation and General Water Use)

WIN Site ID 1536

(61118003) 1558

(61118025) 1559

(61118026)

Na (sol) (mg/L)

<115 (sensitive crops) 115 – 230 (moderately sensitive crops) 230 – 460 (moderately tolerant crops)

>460 (tolerant crops)

- 125 -

NO3-N

(sol) (mg/L)

5 (LTV Total Nitrogen) - - 0.6

Public Drinking Water Supply 2.5.3

The site is not located within the Bunbury Water Reserve drinking water source protection plan area (DoW, 2008).

Contaminated Sites 2.5.4

The DER Contaminated Sites database was searched for known contaminated sites within or adjacent the site (DER, 2015). No registered sites were found within or in close proximity to the site.

2.6 Vegetation

The site contains patches of remnant coastal vegetation mapped on a regional scale as part of the Quindalup Complex. The vegetation is degraded through historical weed invasion, edge effects, uncontrolled access and clearing.

The Environmental Review prepared for the Greater Bunbury Region Scheme did not identify remnant vegetation being present or any recorded Declared Rare Flora (DRF) or threatened floristic communities occurring within or adjacent to the site (WAPC, 1999).

Further detail on the vegetation on the site is provided in the Environmental Summary Report (Coterra Environment, 2015).


3.0 STORMWATER MANAGEMENT

Stormwater will be managed through the implementation of Water Sustainable Urban Design (WSUD) principles and Best Management Practices (BMPs) to address increased runoff as a result of increased impermeable areas.

3.1 Existing Drainage

As previously stated, Lot 66 is currently undeveloped with some remnant vegetation. Runoff flows in a south-westerly direction towards Scott Street and the Ocean Drive drainage system. Any runoff exceeding the capacity of the road drainage system flows into the Ocean Drive road reserve before ultimately discharging across the foreshore into the ocean. There is currently no drainage infrastructure within the site boundary.

The City of Bunbury has not advised of any pre-existing capacity issues with the Ocean Drive road drainage system.

3.2 Proposed Drainage Strategy Overview

Drainage Objectives and Targets 3.2.1

The site will manage stormwater by addressing the quantity and quality of runoff resulting from increased impermeable areas post development. The design objectives and criteria outlined in BUWM are summarised in Section 1.3.

The design of the stormwater drainage system at the site will also comply with CoB stormwater guidance, outlined in the sections below. CoB Development Engineer Damien Morgan (pers. comm) has provided the following general advice relating to the city’s stormwater drainage requirements:

1 m3 of storage must be provided for every 65 m2 of impervious area on the

site.

To manage any larger storm events it is expected that overland drainage

flows can follow existing major flow routes.

The City are open to the use of any proprietary stormwater drainage

infiltration products (such as Atlantis Cells), if they are suitable for purpose

and are shown to be suitable for vehicle and other loadings where required.

The CoB requires an additional 1 m3 of storage per 65 m2 of impervious area where the site is commercial and greater than 1,500 m2 in area. Where mixed use development is proposed, the CoB has advised that the additional storage requirement is assessed on a case-by-case basis.

Previous liaison by the project engineers with the City of Bunbury regarding the larger neighbouring lot, lot 497 indicated that this requirement was aimed at large industrial sites and large carparking areas, and as such this requirement was not considered applicable for the mixed-use development on Lot 497 (Daniel Gleason, pers.comm). On this basis, the additional storage requirement is not considered


applicable to Lot 66, and has not been included in the storage requirements outlined in this SMS.

Drainage Overview 3.2.2

Based on the requirements outlined above, the sites drainage strategy will comprise of the following:

Water Quantity:

Runoff from events up to 100 year ARI will be managed on site, and

discharged at a rate no greater than pre-development flow rates.

Discharge from the site during larger events will be into the existing

drainage network on Ocean Drive.

Onsite Conveyance:

Events up to the 100 year ARI event will be conveyed in a new onsite piped

network.

Water Quality:

Retention and infiltration of small (1 year ARI) events on site. It is noted that

the CoB requirement of 1 m3 of storage per 65 m2 of impervious area is

approximately equal to the 1yr (1hr) ARI and the 15 mm rainfall event.

Water quality treatment will be provided in infiltration areas, which will have

soil amendment and be vegetated with seeds and sedges.

Stormwater will be infiltrated or discharged within 96 hours to prevent

disease vector and nuisance insects.

3.3 Catchment Areas

As the proposed development is multiple storey, the uppermost level has been used to derive the drainage catchments. Based on the current development concept plans provided in Appendix A, the site will be comprised of two separate catchments, as shown in Figure 4:

Catchment 1 (roof runoff) – this catchment is approximately 1,860 m2 and is

comprised of residential and commercial buildings. The runoff from this

catchment is considered clean as it will have no other function.

Catchment 2 – this catchment is approximately 774 m2 and is comprised of

exposed carparking areas, a communal courtyard and swimming pool, and

hardstand areas such as footpaths.

It is noted that it is assumed that runoff pervious or impervious areas outside the

lot boundary will discharge to the nearest road drainage network.


3.4 Stormwater Events

1 Year ARI Event 3.4.1

Runoff generated in the 1 year ARI event will be fully infiltrated on site. The runoff will be conveyed via the piped the network to infiltration areas, as outlines below:

Within catchment 1, runoff will be captured from the roofs of the

commercial and residential buildings and infiltrated in soakwells.

Within catchment 2, runoff will be treated and infiltrated within a raingarden

or series or raingardens located on the western boundary.

The storage volume for the 1 year ARI event has been calculated as the CoB

requirement of 1 m3 of storage per 65 m2 of impervious area. This is approximately

equal to the Department of Water requirement to retain stormwater from

impervious areas generated by a rainfall event of 15 mm (and similar to the 1yr

(1hr) ARI event).

5 Year ARI Event and above 3.4.2

Runoff generated up to the 100 year ARI event will be conveyed via the piped network to attenuation areas within each catchment, prior to being discharged to the Ocean Drive piped network at pre-development flow rates (discussed further in Section 4.5).

Within catchment 1, large events will be attenuated and infiltrated in soakwells/underground storage prior to being discharged to the Ocean Drive drainage network at pre-development flow rates (discussed further in Section 3.5).

Within catchment 2, runoff will discharge to the raingarden. When the capacity of the raingarden is exceeded runoff will overflow to the soakwells/underground storage system, where it will be infiltrated and attenuated prior to discharge to the Ocean Drive network at no more than pre-development flow rates (discussed further in Section 3.5).

Lot levels will be elevated at least 500 mm above the 100 year ARI design stormwater top water level within the infiltration basins/areas (to be determined at detailed design stage).

3.5 Storage Sizing and Flow Rates

Preliminary calculations have been undertaken by KCTT to estimate pre-development flow rates and the minimum storage required to ensure that post-development flow rates do not exceed pre-development flows.

Due to limited available information on the existing stormwater network, the project engineers have made a number of assumptions in these calculations. These assumptions are summarised below, and are listed in full in Appendix B.

Runoff from the site can be discharged into the existing pipe network on

Ocean Drive at pre-development flow rates.


The outlet to the ocean is located in the vicinity of Baldock Street. Drop manholes have been used in areas of steep topography. Conservative pipe grades of 1 in 200 have been used.

The pre and post development peak flow rates are provided in Table 7.

Table 7 Pre and Post Development Flows

ARI event Pre-development flow (m3/s)

Post-development flow (m3/s)

1 year 0.032 0.00 – Retained on site 5 year 0.055 0.055

100 year 0.111 0.111

The drainage calculations have indicated that a storage volume of 56.25 m3 is required to adequately attenuate post-development runoff in line with BUWM guidelines. Storage Requirements

The CoB and Better Urban Water Management (BUWM) storage requirements for the site are outlined in Section 3.2 and are summarised in Table 8 below.

Table 8 Storage Requirements

CoB Minimum Requirement

Area Storage

Required Comments

1 m3 per 65 m2 of impervious

area

Total site area is 2,850 m2.

Approximate impervious area

is 2,634 m2

40.5 m3

Based on current concept design. Development assumed

to be approximately 92% impervious.

BUWM Requirement Additional

Storage Required

Comments

Attenuation of the 5 year ARI event to pre-development rates

8.35 m3

(48.85 m3 total)

This runoff will be attenuated in soakwells and/or

raingardens within each catchment prior to discharge

Attenuation of the 100 year ARI event to pre-development rates

15.73 m3

(56.23 m3 total)

This runoff will be attenuated in soakwells and/or

raingardens within each catchment prior to discharge

Storage Areas 3.5.1

The total required storage volume will be split to reflect the runoff from each catchment. The indicative areas to be provided are outlined in Table 9 below. Please note that the exact location of these areas will be confirmed during detailed design.

Table 9 Storage Areas

Catchment Storage type Approx. storage

volume Indicative Area

(m2)

1 Soakwells /underground

storage (assumed 2m deep) 39.72 m3 33 m2


3.6 Water Quality Treatment

Gross Pollutant Traps 3.6.1

Where required, gross pollutant traps and/or other management devices will be used within the drainage system to manage litter, leaves and other gross pollutants.

Vegetation 3.6.2

The majority of pollutants are transported in the smaller rainfall events, typically less than the 1 year ARI event. The raingarden will be vegetated to help prevent erosion, maintain soil infiltration, restrict water flows and remove pollutants (particularly nitrogen). The sedges and plants will be appropriately selected based on their intended function using native vegetation as much as possible.

Soil Amendment 3.6.3

The soils underlying the site are likely to be weakly to moderately adsorbing of phosphorus (see Section 2.4.2). To ensure maximum phosphorous is retained prior to infiltrating to groundwater, 300 mm of a soil with a PRI of approximately 10 will be applied to the base of the raingarden. This amended soil layer will ensure that there is an increased capacity for the soil profile to adsorb and bind phosphorus to the soil profile, removing it from the stormwater prior to reaching groundwater.

Non-Structural Controls 3.6.4

Non-structural controls can be used to provide additional stormwater quality management and can include raising awareness, establishing operation and maintenance activities and controlling land use and management.

3.7 Public Open Space

Based on the current development concept plan there will be no public open space provided within the development.

The rain garden will be located on the site’s southern boundary, however as this provides a stormwater function, it does not require ongoing irrigation. Sedges and vegetation planted within the infiltration areas will be selected for their specific stormwater design function.

There may be some very minor landscaping (garden beds) within the carpark and pool area. This will be irrigated with scheme water.

2 Raingarden (assumed 0.5m

deep) 11.61 m3 23 m2

2 Soakwells/underground

storage (assumed 2m deep) 4.9 m3 2.5 m2

Total Storage 56.23 m3


4.0 GROUNDWATER MANAGEMENT

4.1 Proposed Earthworks

As outlined in section 2.3, Lot 66 slopes from its north-eastern corner to its south western corner, ranging from approximately 17 mAHD to 11 mAHD. Some earthworks and cut and fill/ re-contouring will be required to form flat building pads. The detailed earthworks plans will be provided at detailed design stage. It is anticipated that cut and fill will use existing site sands where possible.

Separation Distances 4.1.1

4.1.1.1 Lot Levels to Groundwater

Finished lot levels will be determined at detailed design stage to match the final building shape and layout at the site. As such, the exact range in separation distances between peak groundwater level and finished lot levels cannot be determined at this stage. However there is currently significant separation to groundwater on site (approx. 10.5 - 16.5 mAHD), therefore the required separation distances to groundwater, as per the BUWM guidelines, are anticipated to be sufficiently achieved.

The minimum levels for the required separations are provided below, and the final detailed design will meet the following criteria:

Building pads will be at least 1.2 m to peak groundwater levels - at a minimum

of approx. 1.8 mAHD.

Consideration will be given to the distance between infiltration zones and semi basement areas.

4.1.1.2 Infiltration Areas to Groundwater

The proposed raingardens are likely to be located along the southern boundary of the site, in the lowest elevation area. Currently the separation to groundwater in that location is approximately 10.5 m, and the total depth of the raingarden is only likely to be in the order of 1 m (0.5 m maximum water level plus 0.5 m freeboard to manage flood risk).

This allows significant separation to achieve the required separation distances to groundwater as per the BUWM guidelines. The minimum levels for the required separations are provided below, and the final detailed design will meet the following criteria:

The base of the raingarden will be a minimum of 300 mm above peak

groundwater levels - at a minimum of approx. 0.9 mAHD. As detailed above,

this is significantly below the current topography at the proposed infiltration

locations.


4.1.1.3 Soakwell Base to Groundwater

Soakwells will be used to provide additional on-site storage and infiltration. In order to remain effective a minimum separation of 0.5 m is recommended between the base of the soakwell and maximum groundwater levels.

As indicated above, groundwater separation at the site ranges from approximately 10.5 - 16.5 mAHD. This equates to a minimum separation distance of 8.5 m from the base of the 2 m high soakwells to maximum groundwater levels (assuming soakwells are at surface).


5.0 IMPLEMENTATION

The effective implementation of the SMS requires ongoing involvement by the relevant stakeholders. As agreed with the CoB, a Stormwater Management Plan (SMP) will be required at subdivision stage. The requirements of the SMP will be confirmed with the CoB prior to preparation of the plan.

The future roles and responsibilities associated with the site are summarised in Table 10.

Table 7 Roles and Responsibilities for Implementation

Principles Role Responsibility Timeframes

Stormwater Management

Detailed design of stormwater drainage system in line with the criteria in this document

Proponent Prior to construction

Construction of stormwater infrastructure including water quality measures

Proponent At construction

Maintenance of he drainage infrastructure

Proponent Ongoing by owner or strata body

Groundwater Management

Detailed earthworks plan in line with the criteria in this document


Water Quality Management

Detailed design of water quality management features (i.e. rain-gardens)



6.0 REFERENCES

Bureau of Meteorology (2015). [online] http://www.bom.gov.au/climate/averages/tables/cw_009194.shtml (accessed 11 May 2015)

Churchward and McArthur (1978) Darling System Landforms and Soils. Department of Conservation and Environment, Perth, WA

Coterra Environment (2013) Environmental Assessment Report for Lots 1, 2 and 76 Ocean Drive, Bunbury. Prepared for TPG Pty Ltd on behalf of AET Limited.

Coterra Environment (2015) Environmental Summary Report. Lot 66 Ocean Drive, Bunbury. Prepared for TPG Pty Ltd

Department of Environment and Regulation (2013) Contaminated Sites database. (Accessed online 8/1/15)

Department of Water (2004-2007). Stormwater Management Manual for Western Australia: Non-Structural Controls, Non-Structural Controls Best Management Practices Guidelines.

Department of Water (2015a). Perth Hydrogeological Atlas. [online] http://www.water.wa.gov.au/idelve/hydroatlas/ (accessed 7 May 2015)

Department of Water (2015b). Perth Groundwater Atlas. [online] http://www.water.wa.gov.au/idelve/gwa/ (accessed 7 May 2015)

Department of Water (2015c). WIN database Water Resources Data. DR32170

Landgate (2014) WA Atlas map of Acid Sulfate Soils Risk (accessed online 15/06/15)

WA Atlas (2015). Acid Sulfate Soil Mapping. [Online] https://www2.landgate.wa.gov.au/bmvf/app/waatlas/ (accessed on 7 May 2015)

Western Australian Planning Commission (2008). Better Urban Water Management.

Western Australian Planning Commission (1999) Greater Bunbury Region Scheme. WAPC, Perth.

FIGURES

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´ Source: Imagery - Landgate, 2014

Scale: 1:200,000 @ A3 GDA 1994 MGA Zone 50 Figur

e 1

Job: TPGCPN02Doc: 001Date: 26.06.15Ph: (08) 9381 5513Fax: (08) 9381 5514E: [email protected]

SITE LOCATION

The Planning GroupSTORMWATER MANAGEMENT STRATEGYCENTRAL PRECINCT NORTH, LOT 66 OCEAN DRIVE BUNBURY

0 500250m

SITE LOCATION

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GeologyQhsm, SAFETY BAY SAND: Mobile dunes

Qhs, SAFETY BAY SAND: Calcareous quartz sand dunes


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Source: Cadastre - Landgate, 2015 Orthophoto - Landgate, 2014 Contours - Landgate, 2015 Geology - DoIR, 1999

Scale: 1:1,000 @ A3 GDA 1994 MGA Zone 50

TOPOGRAPHY AND GEOLOGY


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Scale: 1:7,500 @ A3 GDA 1994 MGA Zone 50 GROUNDWATER


INDIANINDIANOCEANOCEAN

APPENDIX A – DEVELOPMENT CONCEPT PLANS

LLOYD PICKWELL

APPENDIX B – ENGINEERING DESIGN SYNOPSIS AND CALCULATIONS

| Kleyweg | Civil | Traffic | Transport |

KCTT (Trading As KC Traffic and Transport Pty Ltd)

| ABN 35 148 970 727 | correspondence: 830B Beaufort Street, Inglewood WA 6052 | phone: 08 9272 7770 |

mail: [email protected] | Web site: www.kctt.com.au |

24.06.2015

Our Ref: KC00276.000 L01 – Drainage Calculations

Coterra Environment

2 / 460 Roberts Road

Subiaco, WA 6008

Attn: Carrie Hopkirk

RE: Lot 66 Ocean Drive, Bunbury:

Drainage Calculations and Assumptions made by KCTT

Dear Carrie,

This letter details the pre and post development flows for Lot 66 Ocean Drive, Bunbury. Much like the previous

development, Lot 497 Ocean Drive, there is limited information available for the proposed development, in terms of

detailed engineering Drawings of the existing infrastructure. It should be noted that the calculations undertaken for

this development have been based on an area of assessment, and have not considered, nor sized infrastructure for

future development upgrades upstream of Lot 66 Ocean Drive.

Unlike Lot 497 Ocean Drive, there is no Stormwater infrastructure running through the subject site. Further, there is

no useful existing infrastructure within the road reserves that surround the proposed development. However,

infrastructure on the Upper Esplanade is considered to be of use, but has been previously included in calculations

for Lot 497 (as well as the associated runoff). The development of Lot 66 Ocean Drive will require the installation of

new infrastructure within the road reserves that will connect with the infrastructure in Lot 497, eventually discharging

at an outlet structure at the end of Baldock Street.

The calculations for the post development scenario were based on the concept design Drawings provided by Lloyd

Pickwell Architecture. KCTT note that there will be a 5m offset on the development side of Ocean Drive for Lot 66,

this area will be more than sufficient to treat and infiltrate the runoff from impervious areas within the development.

Further, it is deemed suitable as it is located at the low point of the subject site, thus less earth working will be

required to locate a rain garden in the proposed location. Roof runoff will be conveyed via soak wells placed within

the development. The geology and groundwater levels within the subject site support the installation of soak wells.

The calculations of the pre-development and post development flows for Lot 66 Ocean Drive were much more

simplistic than that of Lot 497 Ocean Drive. Lot 497 calculations considered utilizing existing infrastructure within

the vicinity of the development to convey flows from the 5 and 100 year ARI events, eventually discharging at the

outlet structure located at the end of Baldock Street. Thus, this had to be factored into the calculations. The ultimate

strategy for Lot 66 Ocean Drive involves connecting into the proposed infrastructure constructed for Lot 497 Ocean

Drive. Consequently, Lot 66 will aim to utilize the existing infrastructure downstream, however will not need to model

it in calculation. That being said, infrastructure along Ocean Drive may be required to be upgraded from a 600mm

diameter pipe, to a 750mm diameter pipe. Though determination of these upgrades can be determined in detailed

design, and whether these upgrades must be undertaken does not affect the calculation of pre and post development

flow rates for Lot 66 Ocean Drive, nor does it affect the calculation of storage requirements.

It should be noted that the abovementioned strategy will restrict the timing of development of Lot 66 Ocean Drive,

as it can only be developed at the time of development of Lot 497 Ocean Drive, or afterwards.





Calculation of the pre and post development rates for Lot 66 Ocean Drive have been summarized below in Table 1.

Additionally, the storage requirements for the development have been summarized in Table 2. These storage

volumes are based on the City of Bunbury requirement of 1m3 of storage for 65m2 impervious area. Additionally, the

storage volumes also account for compliance of Better Urban Water Management (BUWM) criteria, to attenuate the

5 and 100 year ARI events to pre-development rates.

Table 1 – Pre and Post Development Flows for Lot 66 Ocean Drive:-

ARI Event Pre-development flow (m3/s) Post-development flow (m3/s)

1 year 0.032 0 – (Retained/Infiltrated within

Rain Garden on site).

5 year 0.055 0.078

100 year 0.111 0.155

Table 2 – Storage Requirements for Lot 66 Ocean Drive:-

Criteria 1 Year ARI Event 5 Year ARI Event 100 Year ARI Event

CoB Criteria: 1m3 of

storage per 65m2 of

impervious area

43.85m3 - -

5 year - 8.35 m3 -

100 year - - 15.73 m3

Total Storage

Requirement per event 43.85 m3 8.35 m3 + 1 year storage

= 52.20 m3

15.73 m3 + 1 year storage

= 59.58 m3

Similarly to Lot 497 Ocean Drive, the storage requirement calculations are based on a conservative estimate a 6

minute duration of the time taken for the runoff to reach storage / treatment location.

The additional storage required can be achieved through the use of soak wells. For a typical 1.8m dia. X 1.2m

depth soak well, 3.0m3 storage can be achieved. This equates to approximately 6 soak wells required for Lot 66

Ocean Drive, these will be spread along the boundary of the site and will be used to store roof runoff.

The assumptions made in the calculations are as follows:-

The City of Bunbury have provided KCTT with Engineering Drawings of the existing drainage infrastructure

along Ocean Drive, completed by GHD in in 2004. We have noticed that there has been some changes,

most notably that the soakage trench illustrated in the Drawings is actually a piped network. We have made

the assumption that the Outlet Structure (flowing into the ocean) was constructed in the location shown in

the Drawings, in the vicinity of Baldock Street.





We have modelled our drainage on the assumption that there will be some upgrades to existing

infrastructure at the time of development of Lot 497 (upgrades of pipe infrastructure along the Upper

Esplanade). To facilitate the flow contribution to the existing infrastructure, some pipes will need to be

sized up, and some existing pipes will require an adjustment of invert levels (both upstream and

downstream). This assumption extends to the proposed infrastructure for the development of Lot 497

Ocean Drive. Pipes along Ocean Drive may require diameter increases to cope with the additional flow from

Lot 66.

Due to the topographical constraints of the subject landholding, we have made the assumption that drop

manholes have been utilized where grades would be too steep to run drainage at a similar grade to the

natural surface. We propose to connect into the infrastructure on Scott Street, the proposed levels along

Scott Street for Lot 497 drainage are treated as set values, therefor connection into this infrastructure may

require ‘drops’ from our infrastructure (Lot 66) to the receiving downstream infrastructure.

Pre development flows have been calculated by hand calculations using information from the Bureau of

Meteorology (rainfall intensity date for the subject site, coordinates: -33.329087, 115.629989), modelling

outflow at the southwest corner of the subject site.

We have obtained contours for the land off the Landgate SLIP Portal, and checked these against contours

from ESINet.

We have made conservative assumptions on the grade of the roads in which stormwater will be conveyed.

We have assumed that some of the drainage along Ocean Drive will be directed through an alternative

drainage network that discharges in a separate location (on the non-development side of Ocean Drive).

Conservative pipe grades of approximately 1 in 200 have been used as much as practically possible in the

post development modelling scenario.

Where not stated, pipe sizes have been assumed for the network in question based on flow expected.

Should you require any additional information, or wish for further clarification of our assumptions, please don’t

hesitate to contact our office to discuss.

Regards,

Daniel Gleason

Graduate Civil Engineer

BEng Hons

email: [email protected]

mobile: 0447 003 918

mailto:[email protected]


KC00245.000 Lot 66 Ocean Drive Drainage Design Page 1 of 2 24/06/2015

Calculation Sheet 1 - Hydrology -

Client: TPGProject: Lot 66 Ocean Drive BunburyJob No: KC00276.000Revision B

UPSTREAM PIT DATA PIT INFLOW BYPASS CUMULATIVECATCHMENTS

U/S D/S PIT Chnge U/S Pit Grade X/fall Road Reserve Lot Runoff Other A.Imp Time ARI Rainfall Q bypass TOTAL Gutter Captured to ByPit Pit TYPE (m) Surface (%) (%) AREA Coeff AREA Coeff AREA Coeff (ha) to Pit Intensity (l/s) from Q Width Flow PIT ? Pass Upstream A.ImpNo. No. Level (m2) (m2) (m2) CA (mins) (yrs) (mm/h) U/S (l/s) Catchment (ha)

0.80 0.35 0.80 6.0 5

MH1 MH2 MH 2.00 16.470 4.00 3.00 - 0 0.35 120 0.80 0.010 6.0 5 98.9 2.6 0.0 2.6 0.6 - 2.6 0.000 0.010MH2 MH3 MH 12.00 16.200 4.00 3.00 - 0 0.35 200 0.80 0.016 6.0 5 98.9 4.4 0.0 4.4 0.7 - 4.4 0.010 0.026MH3 MH4 MH 21.00 15.500 4.00 3.00 - 0 0.35 350 0.80 0.028 6.0 5 98.9 7.7 0.0 7.7 0.8 - 7.7 0.026 0.054MH4 MH5 MH 37.00 15.100 4.00 3.00 - 0 0.35 450 0.80 0.036 6.0 5 98.9 9.9 0.0 9.9 0.9 - 9.9 0.054 0.090MH5 MH6 MH 55.00 13.000 4.00 3.00 - 0 0.35 180 0.80 0.014 6.0 5 98.9 4.0 0.0 4.0 0.7 - 4.0 0.090 0.104MH6 SEP1 MH 62.00 12.550 4.00 3.00 - 0 0.35 400 0.80 0.032 6.0 5 98.9 8.8 0.0 8.8 0.9 - 8.8 0.104 0.136SEP1 SEP2 SEP 0.00 12.000 1.00 3.00 57 0.80 171 0.35 0 0.80 0.011 6.0 5 98.9 2.9 0.0 2.9 0.8 2.9 SEP4 0.0 0.136 0.147SEP2 SEP3 SEP 18.00 11.800 1.00 3.00 45 0.80 135 0.35 0 0.80 0.008 6.0 5 98.9 2.3 0.0 2.3 0.7 2.3 SEP4 0.0 0.147 0.155SEP3 SEP4 SEP 29.00 11.600 2.00 3.00 48 0.80 144 0.35 0 0.80 0.009 6.0 5 98.9 2.4 0.0 2.4 0.6 2.4 SEP4 0.0 0.155 0.164SEP4 OS1 SEP 41.00 11.300 1.00 3.00 105 0.80 315 0.35 0 0.80 0.019 6.0 5 98.9 5.3 0.0 5.3 1.0 5.3 OS1 0.0 0.198 0.217OS1 OS 51.00 11.000 0.50 3.00 - - - - - - - - - - 0.0 #NUM! -MH7 SEP4 MH 60.00 13.000 4.00 3.00 - 55 0.35 400 0.80 0.034 6.0 5 98.9 9.3 0.0 9.3 0.9 - 9.3 0.000 0.034MH8 SEP5 MH 47.00 13.880 4.00 3.00 - 50 0.35 150 0.80 0.014 6.0 5 98.9 3.8 0.0 3.8 0.6 - 3.8 0.000 0.014SEP5 OS2 SEP 41.00 13.500 1.00 3.00 105 0.80 180 0.35 - 0.015 6.0 5 98.9 4.0 0.0 4.0 0.9 4.0 SEP4 0.0 0.014 0.028OS2 OS 51.00 13.200 0.50 - - - - - - - - - - #DIV/0! #DIV/0! -MH9 SEP6 MH 28.00 15.200 0.50 3.00 0 0.80 0 0.35 300 0.80 0.024 6.0 5 98.9 6.6 0.0 6.6 1.2 - 6.6 0.000 0.024SEP6 OS3 SEP 41.00 15.100 0.50 3.00 60 0.80 0 0.35 0 0.80 0.005 6.0 5 98.9 1.3 0.0 1.3 0.6 1.3 SEP4 0.0 0.053 0.058OS3 OS 51.00 15.000 3.00 3.00 - - - - - - - - - - 0.0 #NUM! -GP1 GP2 GP 28.00 16.300 2.00 3.00 0 0.80 50 0.35 200 0.80 0.018 6.0 5 98.9 4.9 0.0 4.9 0.8 4.9 0.0 0.000 0.018GP2 SEP6 GP 35.00 16.100 2.00 3.00 0 0.80 85 0.35 100 0.80 0.011 6.0 5 98.9 3.0 0.0 3.0 0.7 3.0 0.0 0.018 0.029

CONTRIBUTING AREAS HYDROLOGY



Calculation Sheet 2 - Hydraulic Design

Client: TPGProject: Lot 66 Ocean Drive BunburyJob No: KC00276.000Revision A

CATCHMENT DATA PIPE DATA HEADLOSS WATER LEVEL OBVERT LEVELS INVERT LEVELS DEPTHS

U/S D/S U/S Pit A.Imp Tc ARI Inten. Q Lngth Diam HGL Full Pipe U/S Pit D/S Pit Pit K(v2) Pipe Total D/S Pit Up Down Up Down Pipe U/S D/S DepthPit Pit Surface (ha) (min) (mm/h) (l/s) (m) (mm) Slope Velocity Water Level Coeff ----- Loss H/loss Water Stream Stream Stream Stream Grade to to betweenNo. No. Level CA (yrs) (m/s) Level minus K 2g (So L) Level Obvert Obvert Invert Invert Obvert Obvert HGL-Obv

6.0 5 freeboard

MH1 MH2 16.470 0.010 6.0 5 98.9 2.6 10.12 300 169283 0.04 16.320 16.050 4.0 0.000 0.000 0.000 16.050 15.290 15.170 14.990 14.870 84.3 1.18 1.03 0.88 1MH2 MH3 16.200 0.026 6.1 5 98.2 7.0 9.21 300 24174 0.10 16.050 15.350 0.5 0.000 0.000 0.001 15.350 14.530 14.410 14.230 14.110 76.7 1.67 1.09 0.94 1MH3 MH4 15.500 0.054 6.2 5 97.5 14.5 18.32 300 5588 0.21 15.350 14.950 0.5 0.001 0.003 0.004 14.950 13.520 13.380 13.220 13.080 130.9 1.98 1.72 1.57 1MH4 MH5 15.100 0.090 6.4 5 95.9 23.9 17.11 300 2068 0.34 14.950 12.850 2.0 0.012 0.008 0.020 12.850 12.710 12.450 12.410 12.150 65.8 2.39 0.55 0.40 1MH5 MH6 13.000 0.104 6.6 5 94.8 27.4 10.55 300 1569 0.39 12.850 12.400 0.5 0.004 0.007 0.011 12.400 11.570 11.450 11.270 11.150 87.9 1.43 1.10 0.95 1MH6 SEP1 12.550 0.136 6.7 5 94.1 35.6 17.04 450 8192 0.22 12.400 11.850 0.5 0.001 0.002 0.003 11.850 11.070 10.890 10.620 10.440 94.7 1.48 1.11 0.96 1SEP1 SEP2 12.000 0.147 6.8 5 93.2 37.9 16.23 450 7193 0.24 11.850 11.650 0.5 0.001 0.002 0.004 11.650 10.300 10.070 9.850 9.620 70.6 1.70 1.73 1.58 1SEP2 SEP3 11.800 0.155 6.9 5 92.5 39.8 15.51 450 6542 0.25 11.650 11.450 0.5 0.002 0.002 0.004 11.450 9.760 9.570 9.310 9.120 81.6 2.04 2.03 1.88 1SEP3 SEP4 11.600 0.164 7.1 5 91.8 41.7 15.21 450 5945 0.26 11.450 11.150 0.5 0.002 0.003 0.004 11.150 9.150 8.960 8.700 8.510 80.1 2.45 2.34 2.19 1SEP4 OS1 11.300 0.217 7.2 5 91.1 54.9 10.11 600 16163 0.19 11.150 11.150 0.5 0.001 0.001 0.002 11.148 8.820 8.720 8.220 8.120 101.1 2.48 - 2.43 1OS1 11.000 0.5 0.000 0.000 #DIV/0! 11.00 - 0.00 MH7 SEP4 13.000 0.034 6.0 5 98.9 9.3 14.21 300 13555 0.13 12.850 11.150 0.5 0.000 0.001 0.001 11.150 8.740 8.620 8.440 8.320 118.4 4.26 2.68 2.53 1MH8 SEP5 13.880 0.014 6.0 5 98.9 3.8 6.09 300 82518 0.05 13.730 13.350 0.5 0.000 0.000 0.000 13.350 10.070 10.000 9.770 9.700 87.0 3.81 3.50 3.35 1SEP5 OS2 13.500 0.028 6.1 5 98.4 7.8 9.07 600 805324 0.03 13.350 13.350 0.5 0.000 0.000 0.000 13.350 10.010 9.930 9.410 9.330 113.4 3.49 - 3.42 1OS2 13.200 0.000 0.000 #DIV/0! 13.20 - 0.00 MH9 SEP6 15.200 0.024 6.0 5 98.9 6.6 8.55 300 27085 0.09 15.050 14.950 4.0 0.002 0.000 0.002 14.950 13.510 13.400 13.210 13.100 77.7 1.69 1.70 1.55 1SEP6 OS3 15.100 0.058 6.3 5 96.7 15.5 8.51 600 204086 0.05 14.950 14.950 2.0 0.000 0.000 0.000 14.950 13.500 13.420 12.900 12.820 106.4 1.60 - 1.53 1OS3 15.000 4.0 0.000 0.000 #DIV/0! 15.00 - 0.00 GP1 GP2 16.300 0.018 6.0 5 98.9 4.9 11.12 300 49517 0.07 16.150 15.950 2.0 0.000 0.000 0.001 15.950 13.910 13.760 13.610 13.460 74.1 2.39 2.34 2.19 1GP2 SEP6 16.100 0.029 6.1 5 98.1 7.8 16.08 300 19209 0.11 15.950 14.950 0.5 0.000 0.001 0.001 14.950 13.740 13.610 13.440 13.310 123.7 2.36 1.49 1.34 1

Criti

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es



Calculation Sheet 1 - Hydrology -

Client: TPGProject: Lot 66 Ocean Drive BunburyJob No: KC00276.000Revision B

UPSTREAM PIT DATA PIT INFLOW BYPASS CUMULATIVECATCHMENTS

U/S D/S PIT Chnge U/S Pit Grade X/fall Road Reserve Lot Runoff Other A.Imp Time ARI Rainfall Q bypass TOTAL Gutter Captured to ByPit Pit TYPE (m) Surface (%) (%) AREA Coeff AREA Coeff AREA Coeff (ha) to Pit Intensity (l/s) from Q Width Flow PIT ? Pass Upstream A.ImpNo. No. Level (m2) (m2) (m2) CA (mins) (yrs) (mm/h) U/S (l/s) Catchment (ha)

0.80 0.35 0.80 6.0 100

MH1 MH2 MH 2.00 16.470 4.00 3.00 - 0 0.35 120 0.80 0.010 6.0 100 197.5 5.3 0.0 5.3 0.7 - 5.3 0.000 0.010MH2 MH3 MH 12.00 16.200 4.00 3.00 - 0 0.35 200 0.80 0.016 6.0 100 197.5 8.8 0.0 8.8 0.9 - 8.8 0.010 0.026MH3 MH4 MH 21.00 15.500 4.00 3.00 - 0 0.35 350 0.80 0.028 6.0 100 197.5 15.4 0.0 15.4 1.1 - 15.4 0.026 0.054MH4 MH5 MH 37.00 15.100 4.00 3.00 - 0 0.35 450 0.80 0.036 6.0 100 197.5 19.7 0.0 19.7 1.2 - 19.7 0.054 0.090MH5 MH6 MH 55.00 13.000 4.00 3.00 - 0 0.35 180 0.80 0.014 6.0 100 197.5 7.9 0.0 7.9 0.9 - 7.9 0.090 0.104MH6 SEP1 MH 62.00 12.550 4.00 3.00 - 0 0.35 400 0.80 0.032 6.0 100 197.5 17.6 0.0 17.6 1.2 - 17.6 0.104 0.136SEP1 SEP2 SEP 0.00 12.000 1.00 3.00 57 0.80 171 0.35 0 0.80 0.011 6.0 100 197.5 5.8 0.0 5.8 1.0 5.8 SEP4 0.0 0.136 0.147SEP2 SEP3 SEP 18.00 11.800 1.00 3.00 45 0.80 135 0.35 0 0.80 0.008 6.0 100 197.5 4.6 0.0 4.6 0.9 4.6 SEP4 0.0 0.147 0.155SEP3 SEP4 SEP 29.00 11.600 2.00 3.00 48 0.80 144 0.35 0 0.80 0.009 6.0 100 197.5 4.9 0.0 4.9 0.8 4.9 SEP4 0.0 0.155 0.164SEP4 OS1 SEP 41.00 11.300 1.00 3.00 105 0.80 315 0.35 0 0.80 0.019 6.0 100 197.5 10.7 0.2 10.8 1.2 10.0 OS1 0.8 0.198 0.217OS1 OS 51.00 11.000 0.50 3.00 - - - - - - - - - - 0.0 #NUM! -MH7 SEP4 MH 60.00 13.000 4.00 3.00 - 55 0.35 400 0.80 0.034 6.0 100 197.5 18.6 0.0 18.6 1.2 - 18.6 0.000 0.034MH8 SEP5 MH 47.00 13.880 4.00 3.00 - 50 0.35 150 0.80 0.014 6.0 100 197.5 7.5 0.0 7.5 0.8 - 7.5 0.000 0.014SEP5 OS2 SEP 41.00 13.500 1.00 3.00 105 0.80 180 0.35 - 0.015 6.0 100 197.5 8.1 0.0 8.1 1.1 7.9 SEP4 0.2 0.014 0.028OS2 OS 51.00 13.200 0.50 - - - - - - - - - - #DIV/0! #DIV/0! -MH9 SEP6 MH 28.00 15.200 0.50 3.00 0 0.80 0 0.35 300 0.80 0.024 6.0 100 197.5 13.2 0.0 13.2 1.5 - 13.2 0.000 0.024SEP6 OS3 SEP 41.00 15.100 0.50 3.00 60 0.80 0 0.35 0 0.80 0.005 6.0 100 197.5 2.6 0.0 2.6 0.8 2.6 SEP4 0.0 0.053 0.058OS3 OS 51.00 15.000 3.00 3.00 - - - - - - - - - - 0.0 #NUM! -GP1 GP2 GP 28.00 16.300 2.00 3.00 0 0.80 50 0.35 200 0.80 0.018 6.0 100 197.5 9.7 0.0 9.7 1.1 8.5 1.2 0.000 0.018GP2 SEP6 GP 35.00 16.100 2.00 3.00 0 0.80 85 0.35 100 0.80 0.011 6.0 100 197.5 6.0 0.0 6.0 0.9 5.8 0.2 0.018 0.029

CONTRIBUTING AREAS HYDROLOGY



Calculation Sheet 2 - Hydraulic Design

Client: TPGProject: Lot 66 Ocean Drive BunburyJob No: KC00276.000Revision A

CATCHMENT DATA PIPE DATA HEADLOSS WATER LEVEL OBVERT LEVELS INVERT LEVELS DEPTHS

U/S D/S U/S Pit A.Imp Tc ARI Inten. Q Lngth Diam HGL Full Pipe U/S Pit D/S Pit Pit K(v2) Pipe Total D/S Pit Up Down Up Down Pipe U/S D/S DepthPit Pit Surface (ha) (min) (mm/h) (l/s) (m) (mm) Slope Velocity Water Level Coeff ----- Loss H/loss Water Stream Stream Stream Stream Grade to to betweenNo. No. Level CA (yrs) (m/s) Level minus K 2g (So L) Level Obvert Obvert Invert Invert Obvert Obvert HGL-Obv

6.0 100 freeboard

MH1 MH2 16.470 0.010 6.0 100 197.5 5.3 10.12 300 42467 0.07 16.320 16.050 4.0 0.001 0.000 0.001 16.050 15.290 15.170 14.990 14.870 84.3 1.18 1.03 0.88 1MH2 MH3 16.200 0.026 6.1 100 195.8 13.9 9.21 300 6077 0.20 16.050 15.350 0.5 0.001 0.002 0.003 15.350 14.530 14.410 14.230 14.110 76.7 1.67 1.09 0.94 1MH3 MH4 15.500 0.054 6.2 100 194.3 28.9 18.32 300 1407 0.41 15.350 14.950 0.5 0.004 0.013 0.017 14.950 13.520 13.380 13.220 13.080 130.9 1.98 1.72 1.57 1MH4 MH5 15.100 0.090 6.4 100 190.6 47.4 17.11 300 523 0.67 14.950 12.850 2.0 0.046 0.033 0.079 12.850 12.710 12.450 12.410 12.150 65.8 2.39 0.55 0.40 1MH5 MH6 13.000 0.104 6.6 100 188.3 54.4 10.55 300 398 0.77 12.850 12.400 0.5 0.015 0.027 0.042 12.400 11.570 11.450 11.270 11.150 87.9 1.43 1.10 0.95 1MH6 SEP1 12.550 0.136 6.7 100 186.7 70.5 17.04 450 2083 0.44 12.400 11.850 0.5 0.005 0.008 0.013 11.850 11.070 10.890 10.620 10.440 94.7 1.48 1.11 0.96 1SEP1 SEP2 12.000 0.147 6.8 100 184.6 75.2 16.23 450 1834 0.47 11.850 11.650 0.5 0.006 0.009 0.015 11.650 10.300 10.070 9.850 9.620 70.6 1.70 1.73 1.58 1SEP2 SEP3 11.800 0.155 6.9 100 183.0 78.7 15.51 450 1671 0.50 11.650 11.450 0.5 0.006 0.009 0.016 11.450 9.760 9.570 9.310 9.120 81.6 2.04 2.03 1.88 1SEP3 SEP4 11.600 0.164 7.1 100 181.4 82.5 15.21 450 1522 0.52 11.450 11.150 0.5 0.007 0.010 0.017 11.150 9.150 8.960 8.700 8.510 80.1 2.45 2.34 2.19 1SEP4 OS1 11.300 0.217 7.2 100 179.8 108.4 10.11 600 4146 0.38 11.150 11.150 0.5 0.004 0.002 0.006 11.144 8.820 8.720 8.220 8.120 101.1 2.48 - 2.42 1OS1 11.000 0.5 0.000 0.000 #DIV/0! 11.00 - 0.00 MH7 SEP4 13.000 0.034 6.0 100 197.5 18.6 14.21 300 3401 0.26 12.850 11.150 0.5 0.002 0.004 0.006 11.150 8.740 8.620 8.440 8.320 118.4 4.26 2.68 2.53 1MH8 SEP5 13.880 0.014 6.0 100 197.5 7.5 6.09 300 20701 0.11 13.730 13.350 0.5 0.000 0.000 0.001 13.350 10.070 10.000 9.770 9.700 87.0 3.81 3.50 3.35 1SEP5 OS2 13.500 0.028 6.1 100 196.4 15.5 9.07 600 202282 0.05 13.350 13.350 0.5 0.000 0.000 0.000 13.350 10.010 9.930 9.410 9.330 113.4 3.49 - 3.42 1OS2 13.200 0.000 0.000 #DIV/0! 13.20 - 0.00 MH9 SEP6 15.200 0.024 6.0 100 197.5 13.2 8.55 300 6795 0.19 15.050 14.950 4.0 0.007 0.001 0.008 14.950 13.510 13.400 13.210 13.100 77.7 1.69 1.70 1.55 1SEP6 OS3 15.100 0.058 6.3 100 192.5 30.8 8.51 600 51508 0.11 14.950 14.950 2.0 0.001 0.000 0.001 14.949 13.500 13.420 12.900 12.820 106.4 1.60 - 1.53 1OS3 15.000 4.0 0.000 0.000 #DIV/0! 15.00 - 0.00 GP1 GP2 16.300 0.018 6.0 100 197.5 9.7 11.12 300 12422 0.14 16.150 15.950 2.0 0.002 0.001 0.003 15.950 13.910 13.760 13.610 13.460 74.1 2.39 2.34 2.19 1GP2 SEP6 16.100 0.029 6.1 100 195.7 15.6 16.08 300 4829 0.22 15.950 14.950 0.5 0.001 0.003 0.005 14.950 13.740 13.610 13.440 13.310 123.7 2.36 1.49 1.34 1

Criti

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es

2/460 Roberts RoadSUBIACO WA 6008

t (08) 9381 5513F (08) 9381 5514

[email protected]

Central Precinct North - Lot 66 Ocean Drive Bunbury - Detailed Structure Plan 71

Appendix F

Infrastructure Servicing Report (KCTT)

72

This page has been left blank intentionally.

June 2015

Rev A

INFRASTRUCTURE SERVICING REPORT

Lot 66 Ocean Drive

Bunbury, Western Australia

INFRASTRUCTURE SERVICING REPORT |

Lot 66 Ocean Drive, Bunbury

PAGE 2

HISTORY AND STATUS OF THE DOCUMENT

Revision Date issued Reviewed by Approved by Date approved Revision type

Rev A 11.06.2015 C Kleyweg C Kleyweg 10.06.2015 Issued for Review

DISTRIBUTION OF COPIES

Revision Date of issue Quantity Issued to

Rev A 11.06.2015 1 (PDF) Gary McCullough (TPG Town Planning, Urban

Design and Heritage)

Document Printed 11/06/2015 3:05 PM

File Name M:\0 - KCTT (Aust)\Jobs\KC00276.000 Lot 66 Ocean Drive Bunbury

ISR\Outgoing\ISR\KC00276.000 Lot 66 Ocean Drive ISR.docx

Author Daniel Gleason

Project Manager Colin Kleyweg

Name of Project Lot 66 Ocean Drive ISR

Name of the Document Lots 66 Ocean Drive Bunbury Infrastructure Servicing Report

Document Version KC00276.000_R01_Rev A

Prepared By: KCTT (Trading as Traffic and Transport Pty Ltd)

ABN 35 148 970 727 |

Postal address: 830B Beaufort Street, Inglewood WA 6052|

Phone: 08 9272 7770 |

Website: www.kctt.com.au |



PAGE 3

Table of Contents

1. INTRODUCTION 4

1.1 SCOPE OF THE ISR 4 1.2 LOCATION AND DESCRIPTION OF PROPOSED DEVELOPMENT 5 1.3 AVAILABLE INFORMATION 6 1.4 NOTES PERTAINING TO THIS REPORT 7

2. EARTHWORKS AND ENVIRONMENTAL 7

3. EXISTING INFRASTRUCTURE 9

3.1 EXISTING SEWERAGE SYSTEM AND PROPOSED REQUIREMENTS 9 3.2 EXISTING WATER SYSTEM AND PROPOSED REQUIREMENTS 10 3.3 EXISTING ELECTRICAL SUPPLY AND PROPOSED REQUIREMENTS 10 3.4 EXISTING GAS SUPPLY AND PROPOSED REQUIREMENTS 12 3.5 EXISTING TELECOMMUNICATIONS AND PROPOSED REQUIREMENTS 12 3.6 STORMWATER DRAINAGE CONSIDERATIONS 12 3.7 ROADWORKS AND GENERAL TRAFFIC ENGINEERING ISSUES 13

4. CONCLUSION, PERCEIVED RISKS, OPPORTUNITIES & MITIGATION STRATEGIES 14

4.1 OPPORTUNITIES AND CHALLENGES 14

Appendices

Appendix A – KCTT ISR Graphics for Lot 66 Ocean Drive, Bunbury Back Beach.



PAGE 4

1. INTRODUCTION

KCTT have been requested to provide an infrastructure servicing report (ISR) as part of the proposed development

for Lot 66 Ocean Drive, Bunbury. This proposed development will become part of the Back Beach Tourism Precinct.

The subject site is under the jurisdiction of the City of Bunbury. This report provides an assessment of the proposed

development’s feasibility from the perspective of infrastructure servicing and the general requirements for urban

development, including earth working, excavation of trenches, utilities servicing, and provision of roads and car-

parking.

Given the above, our report is laid out under the following sections: -

Section 1 Introduction (Including Report Layout and Location Information)

Section 2 Earthworks and Environmental

Section 3 Existing Major Infrastructure & Potential Major Infrastructure Requirements

Section 4 Conclusion, Perceived Risks & Potential Risk Mitigation Strategies

1.1 Scope of the ISR

The information provided herein addresses the civil engineering aspects of potential mixed-use development of the

subject landholding and assesses the availability of existing, and or proposed, infrastructure assets in proximity to

the subject site. Rational engineering judgement has been exercised to provide advice on the potential infrastructure

requirements to support the proposed development. The professional advice provided in this report is preliminary

and subject to change in the planning, detailed design and implementation phases of the project. Furthermore, this

report assesses the existing conditions of the study area and describes the general site works required for the nature

of works involved. Moreover, the report discusses the upgrade/connection requirements for the proposed

developments in terms of major infrastructure, which includes: -

Groundwater - General discussion on groundwater and site soil conditions from the Department of Water’s

Mapping Systems for the Bunbury Region.

Site works and Earthworks - General discussion on the likely clearing requirements, and any site specific

earth working requirements including discussion regarding the likely requirements for site retaining walls.

Roads – The proposed development concept indicates multi-story dwellings on Lot 66, consequently there

is no provision for internal roads in this development. It is important to note that the plan provided by

Lloyd Pickwell Architecture is indicative. Access / Egress to the multi-story parking facilities within the

development is to be provided via crossover off Scott Street and the Upper Esplanade. The general

requirements for road upgrades and crossover specifications will be considered in this phase.

Stormwater – The City of Bunbury (CoB) will provide the technical requirements for storm water drainage.

Conveyance of internal road drainage and treatment of 1, 5 and 100 year storm events are likely to be the

key requirements. Utilisation of the existing piping infrastructure in the vicinity of the subject landholding

will be assessed, detailed drainage calculations (provided by KCTT) will be used to determine the likely

infrastructure upgrades that would be required to facilitate development on Lot 66, and to connect into the

existing drainage system. We will review requirements for storage of stormwater drainage within the site



PAGE 5

boundaries, through detention / infiltration methodologies. Any amendments to the City of Bunbury’s

stormwater drainage system due to road works in the vicinity of the subject site will also be discussed.

Wastewater (Sewer) – The extension of wastewater infrastructure (sewer) is not applicable for this

development. Though this is largely dependent on the ability to service the proposed development off the

existing connection that runs along Ocean Drive. Due to the locality of some of the retail shops, it may be

reasonable to suggest that an additional line could be run off Scott Street, collecting wastewater and

bringing it back down to the existing infrastructure on Ocean Drive.

Potable Water Supply – As above for sewer, but an extension off the existing main is not as likely as the

above.

Power – KCTT will assess the closest possible location for the connection of services to support the nature

of the proposed development over Lot 66 Ocean Drive. Further, we will review the Western Power Network

Capacity Model and the ‘Dial Before You Dig’ (DBYD) data to enable us to provide general commentary for

the extension of Western Power assets.

Telecommunications – KCTT will provide general commentary relating to telecommunications

requirements based on the information available as at the date of this reporting. We will discuss potential

connection points based on the information identified from the DBYD data.

Gas – Discuss potential opportunities for the connection and extension of gas at the expected connection

points along Ocean Drive, Scott Street, or the Upper Esplanade.

1.2 Location and Description of Proposed Development

The subject site is bounded by the Scott Street to the south, vacant and undeveloped land to the north (Lot 76), the

Upper Esplanade to the east, and Ocean Drive to the west.

On the western side of the subject site is the Bunbury Back Beach with the Surf Club while on the eastern side of the

subject site is the Bunbury Senior High School. Adjacent to the northern boundary are tennis and basketball courts

provided predominantly, but not exclusively for the Bunbury Senior High School. The subject site is currently vacant

with some pockets of dense vegetation and some steep sandy banks.

Lot 76 to the north has been classed as a special use zone 1, this lot also forms part of the Back Beach Tourism

Precinct and could potentially be a hotel, potential tourism hub and / or residential development. Surrounding land

uses include Back Beach and regional parkland (immediately adjacent to the west), Bunbury Surf Life Saving Club

(SLSC) to the northwest, a beachside restaurant (Noowoh) also to the northwest, and Victoria Street the CBD’s main

street and café strip approximately 1 kilometre to the northeast. An illustration of the subject landholding and the

surrounding land use is shown in Figure 1 below:-



PAGE 6

Source: City of Bunbury Back Beach Tourism Precinct Plan

1.3 Available Information

Dial Before You Dig – KCTT have collected data through the DBYD service. The information obtained was

the locality and indicative levels of the services required to facilitate development on Lot 66 Ocean Drive.

Aerial Imagery (Nearmaps) – Nearmaps has been utilised to obtain aerial imagery of the subject site. The

imagery obtained will aid in the determination of the vegetation coverage of the area proposed for

development.

Perth Groundwater Atlas – To assess the geologic and hydrologic state of the subject sites, KCTT have

employed the use of the Perth Groundwater Atlas. The database provides groundwater levels, soil

conditions and contour levels for Western Australia.

Landgate SLIP – The use of the Landgate SLIP program will enable KCTT to locate existing utility services

on and around the subject sites, this will complement the DBYD data obtained. The SLIP enabler can also

reveal information about the topography, soil conditions, surrounding environmentally sensitive areas and

planned capital works by the Water Corporations. The topography of the subject site is one of the more

important features to assess given the natural state of the subject landholding.

ESINet – KCTT have reviewed the existing water and sewerage infrastructure within an 800m radius of the

subject site to determine the feasibility of connecting to the existing services.

Site Visit – Daniel Gleason of KCTT has conducted a site visit to inspect the subject site. This site visit was

undertaken at the time of inspecting Lot 497 Ocean Drive, to the south. Colin Kleyweg has previously

inspected the sites as part of KCTT’s earlier reporting for Lots 1, 75 and 76 Ocean Drive, Bunbury Back

Beach.

Aqwest (Bunbury Water Board) – KCTT have reviewed Aqwest’s requirements for the provision of potable

water supplies to the subject site.



PAGE 7

Department of Water Hydrogeological and Geographic Data Atlas’ - Information on expected soil

conditions, AAMGL groundwater levels reviewed from Department of Water mapping. This information is

used as background information only in determining some construction rates.

Note: Some information included in this report has been sought from the relevant regulatory authorities, although it

is important to note that the information given is preliminary in nature. If the proposed development is to proceed,

the client is advised to note that the information received from these authorities is subject to change in the formal

application process.

1.4 Notes Pertaining to this Report

This report has been provided as an input to the Principals’ overall due diligence concerning potential infrastructure

requirements and engineering issues for mitigation regarding the aforementioned landholdings.

This study has been completed as a desktop analysis, prior to the commencement of any level of engineering design.

The following key points should be considered in the usage of this report: -

The development layout has a quantifiable impact upon the cost per lot / yield of development.

There is no evidence of any demolition works having been required on the subject site. The site is vacant

as at the date of this report.

Some feedback has been sought from the various regulatory authorities, however the information received from

those authorities can be subject to change upon formal application.

2. Earthworks and Environmental

The subject site has a reasonable coverage of low-lying vegetation, which is typical of the undeveloped landholding

within the proposed back beach tourism precinct area. Given that the subject site will be situated in an erosive

coastal environment, protection of external environments from wind-blown sands is a key requirement for this

development during the earthworks phase in particular, and the construction phase in general. This report will also

consider the impact from sea level rise, groundwater issues, and Seaspray.

The earthworks for this project are expected to be extensive, given the sites natural topography and the requirement

to develop flat pads for the proposed building structures (inclusive of under croft parking facilities).

The location of stormwater drainage infiltration and underground storage is a key factor for success for this project,

and should be informed in the Detailed Area Plans during the due diligence phase. The City of Bunbury have

confirmed that 1m3 of drainage storage is required for every 65m2 of impervious area on the subject site as described

in Section 3.6. Further, it has been confirmed with the City of Bunbury that, even though the development may be

classed as a mixed-use, the requirement for additional storage for commercial developments is assessed on a case

by case basis and is not applicable for this development.



PAGE 8

Note: The most logical location cost-wise for the storage of stormwater drainage is at the sites lowest topographical

location. Situating the stormwater runoff storage in any other location shall represent a major increase in earth

working requirements across the site and therefore in costs.

Sea Level Rises / Seaspray

The proposed development will not be adversely affected by projected sea level rises in the foreseeable future, the

life cycle of any of the proposed structures will be exceeded at the time where sea level rise should be considered,

not just for this development, but for all developments fronting the coast.

Design and Construction will need to consider the high exposure to coastal conditions and should specify materials

with adequate life-cycle properties. These considerations should also be extended to maintenance and management

requirements of any public infrastructure to be constructed within the development, e.g. the proposed swimming

pool for the development.

Groundwater / Department of Water Geological and Hydrogeological Series Maps

Average depth to groundwater is expected to be around 3 to 5 metres deep according to the information attained

from the Department of Water’s Geological and Hydrogeological Series Maps, this is aided by information obtained

from previous investigations of adjacent sites within the vicinity of the subject site. It is important to note that this

is an annualised average reading and does not consider peaks in the groundwater table. Depth to groundwater

should be confirmed by a detailed geotechnical study prior to commencement of design works for this project.

From a servicing perspective, there will be no deep excavations to connect the proposed development to existing

infrastructure and utilities. However, depth to groundwater should be considered for the deep excavations associated

with the basement car-parking. It is proposed that the development will take advantage of the topographical

challenges of the site and provide underground parking facilities toward the Upper Esplanade side. Considering the

information given in the conceptual design, this places the foundation of the development approximately 2 metres

below the natural surface level, which is still higher than the anticipated groundwater level. It is still recommended

that a geotechnical / hydrogeology report be completed for the site prior to construction, to ensure that proposed

engineering designs comply with clearance to groundwater level requirements.

Surface Geology (Department of Water Geological Series Maps)

The subject site is proposed to be developed over the Perth Basin, which is a thick, elongated sedimentary basin in

Western Australia. Desktop assessment of the subject site locates it within a Leederville Formation, with a dominant

lithology of clay, sand, and coal. Moreover, the formation belongs to the Warnbro Group and occurs as a marine

unit of interbedded sandstone and siltstone, with sediments grading upwards from a coarse basal selection.

The upper layers of the soil geology are likely to be Quaternary and recent, represented by impermanent sand dune

systems and possibly biogenic limestone. Our assessment of the site leads us to believe that the site will be overlain

by weathered free draining soils associated with coastal limestone and other karstic features. As such we expect

that the site will offer good stormwater drainage infiltration characteristics.

Prior to the commencement of any on-site earthworks, a detailed geotechnical study should be undertaken to

determine the likelihood of any karstic (cave) features within the subject site. Similarly, the presence of limestone is

a strong consideration for the development of any basement structures and should also be considered in the

structural design of the building.

This advice is general in nature and is based on information published on the Department of Water’s website.



PAGE 9

Generalised Groundwater Salinity

We do not expect issues with groundwater salinity, however there has been no confirmation of existing groundwater

salinity conditions from the Department of Water. The conditions are expected to exhibit moderate levels of salinity,

given the proximity of the ocean.

Risk of Shallow Acid Sulphate Soils

Desktop investigations of the subject site indicate that there is little likelihood of encountering acid sulphate soils

for the proposed development, at the proposed depths of excavation operations. This is further complimented by

the positioning of the subject site, as its close proximity and site geology support the findings from the desktop

investigation.

Contaminated Sites Database

The Department of Environment and Conservation has a contaminated sites register for known sites in Western

Australia requiring detailed remediation works to be completed. The subject site is not listed on the Department of

Environment and Conservation’s website as requiring remediation; however this does not guarantee that there will

not be isolated pockets of remediation on the subject site due to the past demolition and removal of buildings and

structures on the site, or dumping of materials.

3. Existing Infrastructure

This section documents the locations of existing major services infrastructure pertinent to the re-development of

the subject landholdings, or which needs to be considered due to the proposed works. Existing services are in

immediate proximity of the subject landholdings. These are detailed in the following sections: -

Section 3.1 Existing Sewerage System & Proposed Requirements

Section 3.2 Existing Water System & Proposed Requirements

Section 3.3 Existing Electricity Supply & Proposed Requirements

Section 3.4 Existing Telecommunications Supply & Proposed Requirements

Section 3.5 Existing Gas Supply & Proposed Requirements

Section 3.6 Stormwater Drainage Considerations

Section 3.7 Roadworks & General Traffic Engineering Issues

3.1 Existing Sewerage System and Proposed Requirements

The following information has been obtained through a review of existing services information available through the

Dial Before You Dig and Water Corporation ESINet systems: -

An existing 150mm-PVC diameter sewer main on the eastern side of Ocean Drive immediately adjacent to

the western boundary of the subject site. This main is on a 5.0m alignment within the Ocean Drive road

reserve.

Proposed Infrastructure

The development of the subject landholding does not require any extension to the existing Water Corporation sewer

system. The sewerage system within the development will have to convey waste down toward Ocean Drive, as there



PAGE 10

is no other infrastructure around the subject site. The site will require upgrades to existing connections and

associated infrastructure. This infrastructure will be determined by a hydraulics consultant through negotiations

with the Water Corporation when a formal Development Application is submitted.

3.2 Existing Water System and Proposed Requirements

The following information has been obtained through a review of existing services information available through the

Dial Before You Dig and information provided by Aqwest: -

Existing 100mm-diameter water main immediately adjacent to the proposed development site in Ocean

Drive along the length of the subject site.

Existing 100mm-diameter water main on the eastern side of the Upper Esplanade.

Proposed Infrastructure

The development of the subject landholding does not require any extension to the existing Aqwest water system.

The site will however require upgrades to existing connections and associated infrastructure. This infrastructure will

be determined by a hydraulics consultant through negotiations with Aqwest when a formal Development Application

is submitted.

3.3 Existing Electrical Supply and Proposed Requirements

Western Power information is available through the Distribution Facilities Information System (DFIS) and the

Network Capacity Mapping Tool (NCMT). These resources show the following infrastructure assets are available in

the general vicinity of the subject site: -

Three-phase 22kV high voltage (HV) aerial conductors along the eastern side of Upper Esplanade, south of

Scott Street extending to Baldock Street to the south.

Western Power requires that all new developments be serviced by underground three phase power where three

phase power is available and that this service is provided at one location (i.e. a subject site should only be provided

with one point of connection). Due to the expected loadings from the proposed development configuration, existing

transformers in the local area are not expected to be capable of servicing these sites. It is therefore likely that a new

transformer substation will be required. Western Power will require a transformer on site with the Site Main

Switchboard to be contiguous. As identified in the previous Infrastructure Servicing Report for Lot 497 Ocean Drive,

it is likely a 1MVA transformer / switchgear would be more than sufficient to handle the proposed power loadings

from this site, and the adjacent site. However this should be confirmed when final yields are known and by a qualified

electrical consultant.

The Western Power NCMT shows the area has less than 5MVA of forecast remaining capacity in 2015, however

there are planned upgrade works to the network by 2019 where there is likely to be an increase in forecast remaining

capacity to between 15MVA and 20MVA.

We believe an extension of the 22kV HV network will be required along Scott Street to the development and this

should be factored into any cost estimates for the development of the subject site.



PAGE 11



PAGE 12

3.4 Existing Gas Supply and Proposed Requirements

The development of Lot 66 Ocean Drive would require the addition of a delivery point meter. The existing ATCO

assets are shown in Appendix A and are tabulated below: -

100mm-diameter PVC medium pressure (70 kPa) main on the development side of Ocean Drive.

80mm-diameter PVC medium pressure (70 kPa) main on the western side of Upper Esplanade, running up

along the frontages of the housing adjacent to the Bunbury Senior High School.

100mm-diameter PVC medium pressure (70 kPa) main on the northern side of Scott Street.

3.5 Existing Telecommunications and Proposed Requirements

Telecommunications services are available by either the NBN or via telephony service providers such as Telstra.

KCTT have reviewed the NBN Mapping Tool and have found that there is no current rollout of NBN services in Ocean

Drive, Bunbury, nor are there any plans to rollout services. This does not preclude application to NBN at the time of

development of this site, however it means that it is more likely at this stage that telephony infrastructure will be

negotiated directly with Telstra. A Telstra main cable runs west down from the Upper Esplanade, along Scott Street

and out onto Ocean Drive.

Fixed line telecommunications are serviced from the Bunbury Telephone Exchange which is located approximately

1.5km to the east of the subject site. Confirmation of servicing would occur at the time of application for servicing.

Telstra charge fees for the design and installation of infrastructure as well as amendments, upgrades and the like to

existing infrastructure located in road reserves (along Scott Street, Ocean Drive, and the Upper Esplanade) external

to development sites such as Lot 66 Ocean Drive, Bunbury.

3.6 Stormwater Drainage Considerations

KCTT have previously undertaken drainage calculations for the development of Lot 497 Ocean Drive, adjacent to the

subject landholding. These calculations aimed to utilize the existing infrastructure, as such significant upgrades were

required to downstream infrastructure to accommodate the additional post-development flow generated from the

site. Similarly, the development of Lot 66 Ocean Drive will connect into the proposed infrastructure network for Lot

497, this may result in a requirement for an upgrade of infrastructure, more specifically upgrades from 600mm

diameter pipes to 750mm diameter pipes along Ocean Drive only.

KCTT have done the detailed drainage calculations for the pre and post development flows for the subject site. Due

to the lack of information available, we have also made a number of assumptions in our calculations. These

assumptions pertain to the longitudinal grades of the roads in which the stormwater would be conveyed, the

catchment areas in the vicinity of the subject site, and upstream and downstream invert levels of existing

infrastructure. We have remained consistent with previous assumptions made in our calculations of drainage for

Lot 497.

The City of Bunbury provided some detailed responses to a series of questions regarding the requirements for the

stormwater drainage design in the Ocean Drive, Bunbury Back Beach precinct. The City’s Engineering Officer,

Damien Morgan confirmed: -



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The City would place a condition on the planning approval that 1m3 of storage is provided for every 65m2

of impervious area on the site. Given the extensive site coverage with buildings, it is likely that up to 80%

of the site will be considered impervious due to building coverage across the site.

The site is classed as a mixed use development, comprising of residential and commercial dwellings.

Discussions with the City of Bunbury has revealed that there will be no extra storage requirement for the

commercial component of the development.

The site may be allowed to have an overflow connection to the City of Bunbury’s drainage system, however

given the soil strata in the area (beach sands) this is not expected to be required for smaller storm events

as infiltration drainage should be sufficient for the land uses proposed.

To manage any larger storm events it is expected that overland drainage flows can follow existing major

flow routes.

The City are open to the use of any proprietary stormwater drainage infiltration products, (such as Atlantis

Cells) if they are suitable for purpose and are shown to be suitable for vehicle and other loadings where

required.

Based on these requirements, KCTT believe that a total of 51.0m3 will be required for on-site storage. This number

has been calculated on the concept design provided by Lloyd Pickwell Architecture, applying the storage

requirements to the impervious areas stated in the Drawings. This storage will include treatment by means of a rain

garden along the frontage of the development (along Ocean Drive). The rain garden will treat / infiltrate the runoff

from the carpark and achieve water quality targets for the development.

The Better Urban Water Management (BUWM) requirement to attenuate post development flows to pre-development

rates will require storage volumes of 16.2 m3 and 31.68 m3 for the 5 and 100 year ARI events, respectively. This

additional storage can be achieved through the use of soak wells around the proposed development. For a typical

1.8m dia. X 1.2m depth soak well, 3.0m3 storage can be achieved. This equates to approximately 10 soak wells

required for Lot 66 Ocean Drive.

The rain garden may be able to store greater amounts than just that of the 1 in 1 year event (51.0m3), and may be

able to provide additional storage for the 5 and 100 year events, this can be determined when details of the rain

garden are provided. That being said, there may be opportunities to retain / infiltrate within the proposed 8m wide

landscaped view corridor. Notwithstanding the above, the runoff from the 5 and 100 year events is predominantly

roof runoff and can be stored in soak wells throughout the site.

There will be a requirement to install site entry pits along Ocean Drive and Scott Street for the proposed development,

the runoff conveyed via this piped system will connect into the infrastructure constructed for Lot 497. Before storage

water on-site enters the existing drainage infrastructure, the City of Bunbury require that this water be treated. The

soak well drainage will flow to a penultimate pit on-site prior to connection to the City of Bunbury’s infrastructure

(with the proposed connection points set along Scott Street). These pits should be fitted with pollution traps to

ensure that water is treated before entering the existing system.

3.7 Roadworks and General Traffic Engineering Issues

KCTT have produced an accompanying report which focuses on the traffic and transportation issues associated with

the development of the subject site (KC00276.000_R01_Lot 66 Ocean Drive Transport Impact Assessment Rev A).

We expect there will be no direct road connection to Ocean Drive for this development, with all road connectivity

from Scott Street and Upper Esplanade. Access and egress to / from the subject site will need to be designed to take

into account the sites topography, in particular for connections to Upper Esplanade. The conceptual design illustrates

access and egress via Scott Street and the Upper Esplanade.



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Pedestrian and cyclist connectivity to Ocean Drive will also need to consider the sites steep topography from east

to west and the requirement to bulk earthwork the site to allow for three rows of development with outlooks across

Ocean Drive to the west.

The existing pathways are predominantly aligned in a north-south direction, linking the Upper Esplanade to the

foreshore and beach. New pedestrian pathways will be constructed for the development of the Back Beach Tourism

precinct to enhance linkages from the precinct to its surrounds (beach, foreshore, CBD etc.). Further, the design of

a new pedestrian pathway along Ocean Drive, fronting the proposed development, will be required to support active

frontages. Any existing pathways, crossings, or lighting that may be affected by the scope of works for the proposed

development will require upgrades to synchronise with the upgrades throughout the precinct.

4. Conclusion, Perceived Risks, Opportunities & Mitigation Strategies

4.1 Opportunities and Challenges

In terms of the natural constraints, the development needs to be responsive to the constraints of sloping coastal

dune land (part of the Quindalup soil-landscape system). The general topography in the Bunbury Back Beach area

can be described as follows: -

Lots 76, 66 and 497 Ocean Drive rise approximately 6-8m eastwards from Ocean Drive to Upper Esplanade

(7.5 – 10% slope);

Lots 1 and 2 Ocean Drive rise up to 4m eastwards from Ocean Drive to Upper Esplanade (5%).

The opportunities that arise from these topographical features are the retention of the coastal landform which offers

extensive outlooks towards the ocean and level change possibilities such as under croft parking and terracing of

public open space (POS). The conceptual design demonstrates that the design for the development embraces the

level changes. Furthermore, there are considerable areas of POS in close (walkable) proximity to the site including:-

The Ocean Drive foreshore;

Ocean Drive Reserve;

Nidja Ngaaland Nedigar Ngoondiny Reserve; and

Pioneer Park.

We believe the following comments are pertinent to the potential development of Lot 66 Ocean Drive, Bunbury and

should be examined in further detail through the due diligence process: -

Sewer

Existing assets are available adjacent to the proposed site and the site is currently connected to the Water

Corporation sewer system.

Water

Existing assets are available adjacent to the proposed site. Connections will be required for fire-fighting

purposes. These connections are managed by Aqwest (Bunbury Water Board).

Power



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It is likely a short external extension of the HV power network will be required to service the proposed

development.

Given the development yields proposed, it is likely that a 1MVA transformer / switchgear will be required.

Consideration should be given to adjacent developments (Lot 497 Ocean Drive), confirmation from an

electrical consultant should be sought as to whether one transformer / switchgear could service the two

developments as opposed to one per development.

Telecoms

Connection to existing services to be determined by Telstra / NBN Co at the time of the development.

Gas

Connection to gas services will be managed through ATCO Gas. The developer will be required to provide

an open trench for ATCO Gas to provide their services. Currently, ATCO Gas do not charge for design

services, or for provision of their infrastructure.

Roadworks, Pedestrian and Cyclist Connectivity

The current Planning, Urban Design and Heritage layout for the site shows one access / egress point to

Upper Esplanade, and one running off Scott Street.

All road and footpath designs need to consider maximum grades for accessibility.

Connectivity with Upper Esplanade needs to consider the existing road levels in Upper Esplanade and the

proposed levels in the internal loop road.

Pedestrian and cyclist paths and connections need to be designed with universal access provisions, cyclist

paths are not recommended along Ocean Drive due to potential safety issues.

Stormwater Drainage

The City of Bunbury requires infiltration drainage and underground / above-ground storage for a minimum

of 1m3 capacity for every 65m2 of building and impervious pavement proposed for the site.

The location for above ground / below ground storage needs to be considered in the future planning. The

logical location based on topography is as close as possible to the south-western corner of the subject

site. If the location for storage of drainage is amended from this location, it increases the requirements for

additional earthworking.

Demolition Works

No demolition works are required.

Environmental

Site visits were undertaken by KCTT to Lot 66 Ocean Drive with an environmental officer from the City of

Bunbury. The environmental officer did not identify any major environmental constraints for development.

Earthworks and Retaining Walls

The subject site features strong topographical relief from east to west, with 4 to 6 metres variation in level

from Upper Esplanade to Ocean Drive.

Significant bulk earthworks are required for the development of the subject site.



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Where changes in existing levels are proposed, consideration for retaining walls will be required.

For frontage of the proposed development (Ocean Drive – development side); retaining walls should be

placed inside the lot to separate the building envelopes and the promenade.

In summary, there are a number of important items to be managed on this project, for the proponents to deliver a

successful outcome, in terms of land usage, product and financial return. The early consideration and actioning of

the items discussed in this report will assist the proponent in the development of the options discussed in this

report.

stormwater management strategy

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