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Attachment I - Updated Engineering Report & SWMP
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ENGINEERING REPORT &
STORMWATER
MANAGEMENT PLAN
Proposed Residential and Commercial
Tenancies
at
30-32 Doonella Street, Tewantin
For
Doonella Street Pty Ltd
A6035/21/ENG/Rev B
May 2021
SR/tk
Prepared by Brah101 Pty Ltd Trading As Alta Projects ABN 91 611 354 511
Civil and Structural Engineering
Project Management
26 Memorial Avenue
P. O. Box 559
Cotton Tree, Queensland, 4558
Telephone: (07) 5475 4125
Facsimile: (07) 5479 1607
e-mail: [email protected]
The content of this document is provided in strict commercial confidence. The content of this
document shall not be disclosed to any third party, without the express written authority of Alta
Projects.
Document Control
Revision A6035/20/ENG/Rev B - Authorised for Issue
Author Signature
No. Date Reviewer Signature Document Status
B May 2021 Will Millroy Stephen Roberts A
R - Revision F - Final A - Approval P - Preliminary
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Full text of sections 2 to 16 (of 120)
Section 2
- Contents - 1.0 INTRODUCTION ......................................................................................... 1 2.0 EXISTING SITE CONDITIONS ................................................................ 2 3.0 BULK EARTHWORKS................................................................................. 2 3.1 Cut and Fill and Erosion/Sediment Control .......................................... 2 3.2 Potential Acid Sulphate Soils (PASS) ....................................................... 2 4.0 SERVICES ....................................................................................................... 2 4.1 Water Reticulation ...................................................................................... 2 4.2 Sewerage ...................................................................................................... 2 4.3 Electricity and Telecommunications ........................................................ 3 5.0 ACCESS ........................................................................................................... 3 6.0 STORMWATER MANAGEMENT ............................................................ 3 6.1 Legal Point of Discharge ............................................................................ 3 6.2 Stormwater Quantity Management ......................................................... 4 6.3 Stormwater Quality Management ............................................................ 5 6.3.1 Proposed MUSIC Model Concept ............................................................... 5 6.3.2 MUSIC Model Input ...................................................................................... 6 6.3.3 MUSIC Model Results ................................................................................... 7 6.3.4 Maintenance .................................................................................................... 8 7.0 CONCLUSION .............................................................................................. 9 APPENDICES APPENDIX A – Existing Survey APPENDIX B – Preliminary Infrastructure Plans APPENDIX C – Water Quality APPENDIX D – Preliminary Detention Tank Calculations
Section 3
1.0 INTRODUCTION
This engineering report and stormwater management plan is lodged in support of
an application seeking to develop residential and commercial tenancies at 30-32
Doonella Street, Tewantin.
The proposed development consists of 4, 2 level buildings with ground floor car
parking. There are 19 residential units and 4 commercial tenancies. No basements
are proposed.
This report addresses relevant engineering issues and should be read in
conjunction with attached preliminary architectural plans and engineering
drawings.
Importantly, this report seeks to address civil engineering issues at a level
appropriate for a Development Application.
Figure 1.1 depicts locality of the proposed development.
Figure 1.1 – Locality Plan
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Section 4
2.0 EXISTING SITE CONDITIONS
The site is located on 30-32 Doonella Street, Tewantin (Lot 32 RP893427 and Lot
903 T 1631). At present the site is vacant and is covered by grassed vegetation.
The site is approximately 2539m2 with a slope from the North to South at
approximately 6.5% towards Doonella Street frontage into existing stormwater
infrastructure. The site historically contained residential/holiday dwellings and
hardstand parking areas.
3.0 BULK EARTHWORKS
3.1 Cut and Fill and Erosion/Sediment Control
The proposed development will require cut to spoil offsite to create a
building platform for the proposed semi-basement and building structures.
Approximately 2,500m3 of spoil will be carted offsite and disposed of
legally.
An erosion and sediment control plan will be prepared prior to the
commencement of construction.
3.2 Potential Acid Sulphate Soils (PASS)
The sites bulk earthworks are above RL 5.0m and therefore an acid sulphate
soils investigation is not warranted.
4.0 SERVICES
4.1 Water Reticulation
The proposed development shall be serviced by an existing 100mm water
main within the northern verge of Doonella Street. A 50mm domestic meter
and 100m fire service meter are proposed by hydraulics consultant Pdd.
Internal sub metering will be provided for commercial and residential
tenancies.
Refer to preliminary infrastructure drawings in Appendix B for service
connection locations.
4.2 Sewerage
The proposed development is to be serviced by the existing 150mm gravity
sewer main which runs along the northern verge of Doonella Street. A
single 150mm stub shall be provided from an existing manhole on the south
east corner. Internal plumbing shall be provided with this development.
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Section 5
Refer to preliminary infrastructure drawings in Appendix B for service
connection locations.
4.3 Electricity and Telecommunications
Power and telecommunications are both available from Doonella Street
overhead network.
5.0 ACCESS
Access to the site will be via two separate commercial crossovers from Doonella
Street into on-grade car parking, located in a semi-basement ground floor.
Carparks, ramps and parking aisles internal to the site have been designed in
accordance with AS2890.1 – ‘Off Street Parking’.
On-grade car parking is proposed to provide necessary off-street car parking.
Refuse collection is proposed from the North-west corner of the site in Sidoni Lane,
as requested by Noosa Council.
6.0 STORMWATER MANAGEMENT
6.1 Legal Point of Discharge
The subject site currently discharges to Doonella Street, the sites legal point
of discharge. In order to replicate existing conditions with regard to
stormwater runoff it is intended to pipe 100% of roofwater and podium
surfaces to a rainwater detention and reuse tank positioned in the eastern
side of the carpark. Roof water and podium drainage collection will be
sized to convey up to and including a 1% AEP event.
The tank will ensure non worsening flows in order to maintain the existing
stormwater properties of the site. This flow will be released via detained
orifice flow from the rainwater detention tank and piped to the existing
stormwater infrastructure along Doonella Street. Environmental flows will
be directed to a Bioretention Basin to ensure reduced pollutant loads are
satisfied as per Water by Design targets (Appendix A – WSUD Design
Objectives for Queensland).
There is a small catchment of the site that bypasses the bio retention basin
due to site levels. It is proposed that the bypass area be treated using
landscaped swales. Refer to Appendix C - MUSIC Model for detailed swale
properties.
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Section 6
6.2 Stormwater Quantity Management
The proposed development will see the percentage impervious area
increase. Un-attenuated this would result in an increase in peak flow
discharge off the site. As a result, a mixed use detention and reuse tank is
proposed to capture runoff, detain flows and slowly release captured runoff
to ensure non-worsening of peak discharges is achieved. Q100 roof podium
flows will be directly connected to the detention tank.
Hydraulic modelling of the attenuation tank is provided in Appendix D.
The model identifies that a 75.4KL (18.4KL detention and 57KL reuse) tank
will ensure discharged flow rates do not increase with this development.
Figure 6.2 shows the assumptions that were used in the calculating an
adequately sized detention tank. Rainfall Intensity Frequency Duration
Data and Temporal Patterns were taken from the Bureau of Meteorology,
using latitude and longitude coordinates provided by Google Maps. Once
all data was imported into excel a rainfall intensity table was created.
Appendix D includes Bom IFD chart and curves for ARR19 rainfall event of
varying frequency.
Figure 6.2
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Section 7
Table 6.2a compares pre and post development flows with the implementation of
the detention tank, with a range of frequent and infrequent storm events for the
ARR19 IFD.
Table 6.2.a: Pre v Post Developed Flows
Refer to Appendix D for full Detention Tank modelling results and data
provided by the Australian Government, Bureau of Meteorology.
6.3 Stormwater Quality Management
In accordance with Noosa Council planning scheme requirements
water quality treatment will be required to be provided. Stormwater
Quality Treatment is proposed to be undertaken via the
implementation of a bioretention basin and swales.
The Healthy Waterways Water Sensitive Urban Design Guidelines
for South East Queensland recommends that stormwater quality
treatment trains are designed to achieve the following reductions in
mean annual pollutant loads, compared to the traditional untreated
case.
80% reduction in Suspended Solids and Gross Pollutants
60% reduction in Total Phosphorous
45% reduction in Total Nitrogen
90% reduction in Gross Pollutants
6.3.1 Proposed MUSIC Model Concept
The concrete roadway and parking and roof water runoff will drain
directly to stormwater pits which will connect into the bioretention
basin, via the detention tank.
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Section 8
The efficiency of the proposed treatment train has been identified by
the Model for Urban Stormwater Improvement Conceptualisation
(MUSIC) developed by Monash University.
A conceptual layout of the treatment train for the site, as input to the
MUSIC Model, is shown in Figure 6.3.
Figure 6.3: MUSIC Model Layout
The location and details of the water quality treatment device is
shown on the preliminary engineering drawings contained in
appendix B.
6.3.2 MUSIC Model Input
The Rainfall Runoff Parameters for the source catchments have been
taken from Water By Design’s – MUSIC Modelling Guidelines,
Version 1.0 2010 and are shown in Table 6.3.2.
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Section 9
Table 6.3.2: Rainfall Runoff Parameters
Rainfall Threshold mm/day 1
Pervious Area Properties
Soil Storage Capacity (mm) 500
Initial Storage (% of Capacity) 10
Field Capacity (mm) 200
Infiltration Capacity Coefficient - a 211
Infiltration Capacity Exponent - b 5.0
Groundwater Properties
Initial Depth (mm) 50
Daily Recharge Rate (%) 28
Daily Baseflow (%) 27
Daily Deep Seepage Rate (%) 0.0
The pollutant load concentrations for each source catchment have
been taken from Table 3.8 of the Water by Design’s – MUSIC Modelling
Guidelines, Version 1.0 2010 and using the concentrations
recommended for residential areas.
The MUSIC Model was run utilising available rainfall data for the
area, being Cooroy, Station 40059. A 6-minute time step analysis was
utilised for rainfall data from 1973 to 1983. Mean annual rainfall for
the area is approximately 1595mm.
The following impervious fractions for various surface types were
used in the model.
Development Type Surface Type Impervious Fraction (%)
Road Reserve Roof/Podium Ground Level
Commercial 75 100 20
6.3.3 MUSIC Model Results
Please refer to attached engineering drawings in Appendix B for
details of the proposed treatment train. Results of the MUSIC model
are shown in Table 6.3.3, which identifies a complying scheme can
be provided with construction of a 28m2 bio retention basin with
27m2 filter area.
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Section 10
Table 6.3.3 Treatment Train Effectiveness
Flow TSS TP TN Gross
ML/y Kg/y Kg/y Kg/y Pollutant
Kg/y
Source Load 3.41 421 1.09 11.0 72.9
Residual Load 2.18 82.9 0.266 3.45 2.38
% Reduction 35.9 80.3 75.5 68.6 96.7
%Target - 80 60 45 90
Reduction
Please note that stochastic generation of pollutant loads has been
enabled so model results will vary slightly between runs.
Refer to Appendix C for MUSIC modelling files.
6.3.4 Maintenance
A recommended maintenance schedule for elements of the water
quality treatment train is outlined in Table 6.3.4.
Table 6.3.4: Treatment Train Maintenance Schedule
Minimum
Device Task Labour Plant Frequency Maximu Failure
per m Mode
Annum Frequenc
y
Bioretentio Inspection Maintenance staff 12 - Grass
n Area 1 man Whipper exceeds
Snipper 250mm in
Maintenance staff Mower height.
Mowing 1 man 12 As Ponding in
required excess of 24
Maintenance staff Shovel & hrs.
2 men Truck Accumulatio
Cleaning 4 n of sediment
As or gross
required pollutants.
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Section 11
Inspection Maintenance staff - 4 As Excessive
1 man during required ponding.
rainfall Downstream
Stormwater events. scouring.
Outlet Discoloured
discharge.
Rectificatio Environmental - As -
Unacceptable
n Consultant required
odours.
7.0 CONCLUSION
The proposed commercial unit development over existing Lot 32 RP893427 and
Lot 903 T 1631 can be readily serviced by existing water, sewer, electrical and
telecommunications infrastructure.
There are no significant earthworks required.
A complying water quality management scheme can be effectively implemented
in accordance with Noosa Council requirements.
With the provision of a roof water attenuation tank, existing discharge flow rates
can be maintained at Doonella Street.
There are no constraints or impediments for the proposed development that
cannot be overcome by ongoing design and construction.
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Section 12
A
Appendix
Existing Survey
[OCR of page images]
Existing Survey
Section 13
TREE LEGEND
(Species i Trunk Dia , Height
TREE — Unknown Species
SO — Sheoak
PINE — Pine Tree
MANGO — Mango Tree
Mac — Macadamia
TT — Tea Tree
POIN — Poinciana
Wat — Wattle
lding Footprint “TREE 0, 30507
THE TITLE BOUNDARIES AS SHOWN HEREON WERE NOT MARKED AT THE TIME
OF SURVEY AND HAVE BEEN DERIVED FROM SURVEY PLANS RP893427 AND L Yo TREE 0.61212
0. LOT BOUNDARIES ARE LIKELY TO DIFFER FROM THOSE SHOWN ON { /
PLAN AND IT IS RECOMMENDED THAT A BOUNDARY RESURVEY BE / 4
CARRIED OUT TO DETERMINE ACCURATE BOUNDARY DIMENSIONS 7
SERVICES SHOWN ON THIS PLAN HAVE BEEN LOCATED ERE POSSIBLE BY \
FIELD SURVEY. IF NOT ABLE TO LOCATED SERVICES HABE BEEN PLOTTED FROM
RELEVANT AUTHORITY RECORDS AND NOTED ACCORDINGLY ON THIS PLAN.
PRIOR TO ANY DEMOLITION, EXCAVATION OR CONSTRUCTION ON THE SITE,
THE RELEVANT AUTHORITY SHOULD BE CONTACTED FOR POSSIBLE LOCATION
OF FURTHER UNDERGROUND SERVICES AND DETAILED LOCATIONS OF ALL
acs
JeWAT 0.41208
Bui lding Footprint
32
RP893427
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DOUONELLA STREET
SIGHT SURVEYS NOTE DETAIL SURVEY OF
) PA OU V S 250/43
ABN 37644791916 LEVEL DATUM — PSM137463 RL5.345 AHD D PARISH NOOSA ~ /
4/59 Gateway Drive CONTOUR INTERVAL — Major 1.0m, Minor 0.2m. | LO/ 32 on RPEGS42/
COUNTY March (/09/1"
Noosaville QLD 4566 & LOT 9O3 ON 116351 Locality Tewantin
Ph 54499644/Fax 54499622, Mob 0412603286 JO & 32 DOONELLA ST ORIGINAL — DRAWING 1125.dw
Email: [email protected] TE WANTIN \WING 5.dwg
Section 14
B
Appendix
Preliminary Infrastructure
Plans
[OCR of page images]
Preliminary Infrastructure
Plans
Section 15
PROPOSED COMMERCIAL DEVELOPMENT
at 30-32 DOONELLA STREET, TEWANTIN QLD
for Donnella Street Pty Ltd
W
Job : A6035/21 DRAWING SCHEDULE Jan 2021
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A6035/21/EW01 EARTHWORKS LAYOUT PLAN | | || || || || || |
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BIN STORE ABOVE
PATH ABOVE
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