norwest private hospital new wing project civil

Taylor Thomson Whitting (NSW) Pty Ltd

Norwest Private Hospital New Wing Project

Civil Engineering Report

for Health Projects International

1 November 2013

131528

Taylor Thomson Whitting (NSW) Pty Ltd Consulting Engineers ACN 113 578 377

48 Chandos Street St Leonards NSW 2065 PO Box 738 Crows Nest 1585 T 61 2 9439 7288 F 61 2 9439 3146 [email protected] www.ttw.com.au

This document is copyright and is the property of Taylor Thomson Whitting (NSW) Pty Ltd and must not be used without authorisation. © 2013 Taylor Thomson Whitting

Civil

SYDNEY

CANBERRA

MELBOURNE

QEC 22375

Health Projects International 131528 Norwest Private Hospital New Wing Project

Taylor Thomson Whitting (NSW) Pty Ltd © 2013 Taylor Thomson Whitting

TABLE OF CONTENTS

Section Page

1.0 INTRODUCTION ........................................................................................................... 3

1.1 PROPOSED WORKS ................................................................................................... 3

1.2 DIRECTOR GENERAL REQUIREMENTS .................................................................... 4

2.0 STORMWATER ............................................................................................................ 5

2.1 EXTERNAL FLOW PATHS AND FLOODING ............................................................... 5

2.2 EXISTING STORMWATER DRAINAGE SYSTEM ........................................................ 5

2.3 PROPOSED STORMWATER DRAINAGE SYSTEM .................................................... 5

2.4 STORMWATER QUALITY ............................................................................................ 6

2.5 CONSTRUCTION PHASE STORMWATER MANAGEMENT ....................................... 6

3.0 CAR PARKING ............................................................................................................. 7

4.0 PAVEMENTS ................................................................................................................ 7

5.0 EXISTING SERVICES .................................................................................................. 7

6.0 CONCLUSION .............................................................................................................. 7



1.0 INTRODUCTION

Norwest Private Hospital is preparing a Development Application (DA) for a new wing at the hospital. This report covers the civil engineering issues at the site to support the DA.

This report has been prepared to accompany an Environmental Impact Statement prepared under Schedule 2 of the Environmental Planning and Assessment Regulation for an application for State Significant Development [SSD 13_6074] . This report specifically addresses the relevant matters associated with the Director General’s Environmental Assessment Requirements issued under Section 78A(8A) of the Environmental Planning and Assessment Act 1979.

1.1 Proposed Works

The proposed works includes a new building on top of the car park in the south-western portion of the site. The proposal also includes an additional car parking area between the existing structure and the site boundary to the south, totalling approximately 1,600 m

2.

Figure 1 shows the basement level plan with the new car park area highlighted in red.

Figure 1 Basement level plan



Figure 2 Proposed new car park location between existing building and retaining wall

1.2 Director General Requirements

Director General Requirements (DGR’s) addressed in this report are listed below.

10) Sediment, Erosion and Dust Controls. Identify measures and procedures to minimise and manage the generation and off-site transmission of sediment, dust and fine particles.

Response – A conceptual erosion and sediment control plan will be prepared as part of the design drawings.

14) Flooding. As assessment of any flood risk on site and consideration of any relevant provisions of the NSW Floodplain Development Manual (2005), including the potential effects of climate change, sea level rise and an increase in rainfall intensity.

Response – Flood risk at the site is minimal due to the fact that the site is near the top of the catchment. Any overland flow is carried by the road network.

15) Drainage. Detail drainage associated with the proposal, including stormwater and drainage infrastructure.

Response – Drainage details are shown conceptually in this report and will be detailed on design drawings. Increase in stormwater discharges will be mitigated though the use of on-site detention and a proprietary stormwater treatment device.



2.0 STORMWATER

2.1 External Flow Paths and Flooding

Flow paths were identified from topographic maps and a site visit. An existing overland flow path travels from Bella Vista Farm to the north, south through the roundabout and southwest on Norbrik Drive. The overland flow path does not have any impact on the proposed works.

No floodways have been identified in the vicinity of the site. Flooding information is not shown on Council’s LEP maps. The site has been assessed through a site visit and does not appear to be flood affected under current and future climate scenarios.

2.2 Existing Stormwater Drainage System

The majority of the existing site drains to an on-site detention (OSD) tank in the southern corner of the site. This tank is 16.3m x 25.0m with a storage volume of 397 m

3. Stormwater

is treated by a CDS P1009L gross pollutant trap before entering the OSD tank. There is a 50 kL rainwater re-use tank adjacent to the OSD tank.

The as-built hydraulic services drawings indicate that the area of the proposed car park bypasses the OSD and discharges via a pit in the southern corner of the site.

2.3 Proposed Stormwater Drainage System

The new building on top of the existing car park will discharge to the existing OSD tank utilising existing stormwater infrastructure. There will be no change to catchment areas or peak flows for this section of the site.

The new car parking area will have a separate OSD tank to meet the requirements of the Upper Parramatta River Catchment Trust’s On-site Detention Handbook, referenced in The Hills Shire Council Design Guidelines. A standard OSD calculation sheet has been included as an attachment to this document. The OSD required is:

• 73 m3 of storage volume;

• A 52 mm orifice on the primary outlet; and

• A 100 mm orifice on the secondary outlet.

The OSD tank will be located at the south-eastern end of the new car park area and discharge to the existing stormwater line running parallel to the site boundary.

Figure 3 Proposed car park drainage

Note that the new car park will not discharge via the existing OSD or re-use systems. It will discharge to the existing system that bypasses the OSD tank. The impact on peak flows is mitigated by the proposed OSD tank, so there will be no impact on the existing drainage network.



Figure 4 Existing stormwater systems outlets, south-eastern corner of the site

2.4 Stormwater Quality

The Hills Shire Council Design Guidelines states that “All proposals are to incorporate WSUD measures”. The document refers to Water Sensitive Urban Design Technical Guidelines for Western Sydney (NSW Government Stormwater Trust and UPRCT, May 2004) for the requirements of WSUD measures. The treatment criteria in the document are outline in Table 1.

Table 1 Stormwater Quality Targets

POLLUTANT/ISSUE

RETENTION CRITERIA

RETENTION CRITERIA

Coarse sediment 80% of average annual load for particles 0.5 mm or less

Fine particles 50% of average annual load for particles 0.1 mm or less

Total phosphorus 45% retention of average annual load

Total nitrogen 45% retention of average annual load

Litter 70% of average annual litter load greater than 5 mm

Hydrocarbons, motor fuels, oils and grease.

90% of average annual pollutant load

A proprietary stormwater treatment device, such as a Humes Jellyfish or a SPEL Basin can be specified to meet stormwater quality requirements. It is recommended that the treatment device be located downstream of the OSD tank to reduce the peak flow through the device and optimise the efficiency.

2.5 Construction Phase Stormwater Management

Construction works are to be carried out in accordance with the “Blue Book” erosion and sediment control requirements. The controls will depend on construction staging and methodology, but will most likely include sediment fences, sandbags around pits and a vehicle wash down. An erosion and sediment control plan will be prepared as part of the design drawings.



3.0 CAR PARKING

A preliminary review of the new parking layout indicates that the aisle width and parking spaces comply with the requirements of AS/NZS 2890.1.

4.0 PAVEMENTS

The pavement will be a ground supported flexible pavement, jointed concrete pavement or a suspended slab on piers subject to geotechnical recommendations.

5.0 EXISTING SERVICES

Existing services have been located through a dial-before-you-dig search. No external services are located in the area covered by the proposed works.

6.0 CONCLUSION

This report outlines the civil development requirements of the proposed new wing at Norwest Private Hospital.

The existing stormwater system can be utilised for the building works, while the new car park will require an OSD tank and a stormwater quality improvement device.

Prepared by: Authorised by:

TAYLOR THOMSON WHITTING TAYLOR THOMSON WHITTING

(NSW) PTY LTD (NSW) PTY LTD

Tim Henderson Stephen Brain

Engineer Technical Director H:\2013\131528\Stormwater\Norwest Hospital Stormwater.doc



Project:

Site Address

Job No:

Designer:

Telephone:

OSD Area:

L.G.A

Site Area 0.16 ha 1,600 m2

Total Roof Area 1E-15 ha 0 m2

Area of Site draining to OSD Storage 0.16 ha 1,600 m2

Residual Site Area (Lot Area - Roof Area) 0.160 ha

Area Bypassing Storage 0 ha

Area Bypassing / Residual Site Area 0.0% 30% Max

No. of Dwellings on Site 1

Site Area per Dwelling 0.160 ha

Roof Area per Dwelling 0.000 ha

Detention

Basic SSR Vols Ext Detention Storage 300 m3/ha Total Storage 455 m

3/ha

Basic SRDs Primary Outlet 40 L/s/ha Secondary Outlet 150 L/s/ha

Residual Lot Capture in OSD Tank 100%

Adjusted SRDs 40 L/s/ha 150 L/s/ha

Detention

Basic SSR Volume Ext Detention Storage 48.00 m3

Total Storage 72.80 m3

Total Rainwater Tank Credits 0.00 m3

0.00 m3

Storage Volume Total 72.80 m3

Storage Volume Ext Detention Storage 48.00 m3

Flood Detention Storage 24.80 m3

OSD Discharges Primary Outlet 6.40 L/s Secondary Outlet 24.00 L/s

RL of Top Water Level of Storage 77.800 m 77.800 m

RL of Orifice Centre-line 76.500 m 76.500 m

Number of Orifices 1 1

Estimated Downstream Flood Level 76.50 1.5 yr ARI 76.50 100 yr ARI

Downstream FL - RL of Orifice Cente-line 0.00 Satisfactory 0.00 m

Design Head to Orifice Centre 1.300 m TWL Ext Detn Storage - RL Orif ice 1.300 m

Calculated Orifice Diameter 52 mm Satisfactory 100 mm

RL of Minimum Habitable Floor Level 81.000 m

RL of Minimum Garage Floor Level 78.000 m

Length of Overflow Weir 1.50 m

Site Runoff Coefficient 0.76

Storm Intensity (5 min 100 yr ARI) 219 mm/h

Peak Flow over Weir 74.0 L/s

Depth of Flow over Weir 97 mm

Freeboard to Habitable Floor 3103 mm

Freeboard to Garage Floor 103 mm

OSD Tank Bypass

Extended Detention

Satisfactory

Satisfactory

Satisfactory

OSD Calculations

Overflow Weir & Freeboard Calculation

Satisfactory

On-Site Detention Calculation Sheet for Upper Parramatta River Catchment

HED Secondary Outlet

Satisfactory

Basic OSD Parameters

Extended Detention

Norwest Private Hospital

Norbrik Drive, Bella Vista

131528

T Henderson

(02) 9439 7288

Satisfactory

Site Data

Satisfactory

Upper Parramatta River Catchment

Baulkham Hills Shire Council

Baulkham Hills Shire Council

11

norwest private hospital new wing project civil

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