BCC BPD Stage 2
Brisbane City Council
25 May 2012
Backflow Investigation
Summary Report
AECOM
BCC BPD Stage 2
Backflow Investigation - Summary Report
Backflow Investigation
Summary Report
Prepared for
Brisbane City Council
Prepared by
AECOM Australia Pty Ltd
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25 May 2012
60238110
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AECOM
BCC BPD Stage 2
Backflow Investigation - Summary Report
Quality Information
Document
Backflow Investigation
Ref
60238110
Date
25 May 2012
Prepared by
Richard Hancock
Reviewed by
Ralf Sieberer
Revision History
Revision
3
Authorised
Revision
Date
Details
25 May 2012
Final For Issue
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Name/Position
Mark Gibbs
Segment Lead –
Water Resources and
Coastal Management
Signature
AECOM
BCC BPD Stage 2
Backflow Investigation - Summary Report
Table of Contents
1.0
2.0
3.0
4.0
5.0
6.0
7.0
Introduction
1.1
Project Background
1.2
Project Structure
1.2.1
Stage 1
1.2.2
Stage 2
1.3
Summary Report
Backflow Investigation – Stage 2 Report
2.1
Identification of Feasible Systems Recommended for Detailed Design and Modelling
2.2
Draft Backflow Management Strategy
2.3
Review of a Range of BPDs
2.4
Summary of Design guidelines
Concept Report – Case Study Areas Detailed Design
Preliminary Design – New Farm C and Milton B
Detailed Design Report – New Farm C and Milton B
Concept Report – Remaining Systems in the Case Study Areas
List of Abbreviations
1
1
1
1
1
2
2
2
7
7
9
10
13
13
13
15
Appendix A
BPD Review Summary and Images
A
Appendix B
Case Study Area Location Maps
B
Appendix C
List of Systems for which Installation of BPDs is Feasible.
C
Appendix D
Maps of Systems
D
Appendix E
Systems Assessed but Excluded
E
List of Figures
Figure 1
Map of systems for which installation of BPDs is feasible and 39 Stage 1 areas
6
List of Tables
Table 1
Table 2
Table 3:
Table 4
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List of systems for which installation of BPDs is feasible
Summary of Review and Evaluation of Backflow Prevention Devices
Summary of Outcomes of Investigations
Summary of Outcomes of Investigations
4
8
11
13
AECOM
BCC BPD Stage 2
Backflow Investigation - Summary Report
1.0
Introduction
1.1
Project Background
1
Following the January 2011 flood event, the Independent Flood Response Review Board recommended that
Brisbane City Council (BCC) study the feasibility of installing devices to prevent backflow from river flooding. BCC
has subsequently commissioned a backflow investigation study that will be delivered in multiple stages.
1.2
Project Structure
1.2.1
Stage 1
The Stage 1 investigations were carried out by MWA Environmental in September 2011 and investigated
measures which could mitigate backflow inundation and outlined the issues involved in assessing the risks of their
implementation. 39 broad areas were identified in the BCC Local Government Area (LGA) which could warrant
more detailed investigation. Stage 1 identified three case study areas which were recommended for initial
investigation and analysis. Stage 1 also included a number of community consultation sessions.
1.2.2
Stage 2
The Stage 2 investigations have involved analysing areas along the Brisbane River in the BCC LGA which
flooded in the January 2011 flood event, to identify drainage systems for which it is feasible to install Backflow
Prevention Devices (BPDs) and which are recommended for detailed design and modelling. The transition from
large areas in Stage 1 to the individual drainage systems in Stage 2 has enabled a detailed examination of the
specific characteristics of each drainage system with respect to the flood levels predicted by BCC, the
topographical layout of the system, the drainage network of pipes or channels and the on-site construction
constraints.
To assist with maintaining the distinction between the results of the Stage 1 and Stage 2 studies, the following
definitions are applied:
-
An ‘area’ is taken to be a large geographical area, often based on suburb boundaries, which may include a
large number of drainage systems. The Stage 1 investigations identified 39 of these areas.
-
A ‘drainage system’ is taken to be a discrete system of pipes and / or channels which are connected
together and which can be investigated with respect to the flooding, drainage network and topographical
features. This Stage 2 report identifies 52 drainage systems for which installation of BPDs is feasible.
For the drainage systems identified as feasible for installation of BPDs, the data for each system have been
collated to produce a draft backflow management strategy, centred on calculation of a ‘Relative Cost Benefit
Ratio’. High level likely installation costs were compared with benefits based on the damages potentially
mitigated by BPDs to produce the Relative Cost Benefit Ratio. While this ratio provides a guide to which systems
provide the highest value, a number of factors will be considered by Council when deciding a priority for
installation of BPDs. These factors may include cost benefit analysis, the number of properties impacted by
floods, the cost of installation, operational issues, previously programmed drainage network upgrades or critical
infrastructure impacted by flood.
The risk assessment aspect of Stage 2 focused on the assessment of the impacts of the additional head loss
created by installation of BPDs to drainage systems. This assessment involved hydrologic and hydraulic
modelling of the potential impacts on the system for low and high tail water river conditions, and for a number of
local storm events.
A literature review of BPDs was carried out of off-the-shelf devices, including consultation with suppliers and
Council, to identify which devices might be suitable for cost effective installation with minimal impact on flooding
and which will require low maintenance.
The three case study areas identified in Stage 1 were examined in detail, and two of the eight drainage systems
were progressed to detailed design, including hydrologic and hydraulic modelling to analyse the potential effects
of the BPDs on the existing system. Concept design, likely cost estimates and hydrologic and hydraulic modelling
were undertaken for the remaining six systems, as well as for five drainage systems identified by Council as being
the highest priority.
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1.3
BCC BPD Stage 2
Backflow Investigation - Summary Report
2
Summary Report
The purpose of this Summary Report is to provide an overview of the investigations carried out as part of Stage 2
of the Backflow Investigation, and to summarise the results of Stage 2. Full details of each investigation are not
reproduced here, but can be found in each individual report.
The Summary Report includes an overview of the following reports which make up Stage 2:
2.0
Backflow Investigation – Stage 2 Report
2.1
Identification of Feasible Systems Recommended for Detailed Design
and Modelling
The Stage 1 investigations identified 39 areas which may have been potentially subject to backflow inundation in
January 2011. The Stage 2 investigations involved analysing areas along the Brisbane River in the BCC LGA
which flooded in the January 2011 flood event, to identify drainage systems to which it is feasible to install
Backflow Prevention Devices (BPDs) and which warrant more detailed investigation and analysis. The transition
from large areas in Stage 1 to the individual drainage systems in Stage 2 enabled a detailed examination of the
specific characteristics of each drainage system with respect to the flood levels predicted by BCC, the
topographical layout of the system, the drainage network of pipes or channels and the on-site construction
constraints.
Aerial photography, 0.25m contours, BCC stormwater network, January 2011 flood extent and BCC Floodwise
Property Reports as supplied by Council were examined to identify areas potentially subject to backflow. Those
areas subject to flooding in January 2011, separated from the river by a levee and linked to the river by BCC
stormwater network were identified as potentially subject to backflow. A total of 52 drainage systems which met
these criteria were identified as feasible for installation of BPDs, and were examined in more detail. A summary
list of the systems is presented in Table 1 and in Figure 1.
A number of areas were examined as potentially subject to backflow but were excluded, because the flooding was
confined to areas which were natural storages for flood waters such as parks along waterways, because the area
did not have a connect to the river via the Council stormwater system, or because the river was able to directly
flood the land directly from the river or creek. These are listed in Appendix E.
The 39 areas proposed in Stage 1 investigations were reviewed in more detail using the data listed above. Some
of these areas were included, some excluded and some amended. Figure 1 shows these 39 areas on the same
map as the systems identified in this study. Where the areas identified in Stage 1 have been included, either in
whole or in part, they have been included on the spreadsheet of systems in Appendix C. Where they have been
excluded, they are included on the spreadsheet of excluded areas in Appendix E
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BCC BPD Stage 2
Backflow Investigation - Summary Report
A number of areas which were identified by members of the public as part of the community feedback processes
have also been reviewed as part of the assessment process. These have been included in either the list of
systems for which installation of BPDs is feasible, or the list of excluded systems in the Appendix E.
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Table 1
4
BCC BPD Stage 2
Backflow Investigation - Summary Report
List of systems for which installation of BPDs is feasible
Streets
Suburb
System Number
Coronation Drive
Auchenflower
AUCH 1-3
Edmondstone Road
Bowen Hills
240
Edward St, Creek St, Margaret St, Alice St
Brisbane
CBD1-4
Apollo Road
Bulimba
202
Carbeen St
Bulimba
201
Coutts St, Kenbury St, Bulimba St
Bulimba
204
Harrison St, Johnston St, Tennyson St
Bulimba
203
Jamieson St, Stuart St
Bulimba
205
Leybourne St
Chelmer
251
Queenscroft St
Chelmer
252
Victoria Ave
Chelmer
226
Eagleview Place
Eagle Farm
247
Brougham Street, Mearns Rd
Fairfield
221
Victoria Street, Sharp St
Fairfield
220
Kenny St
Fig Tree Pocket
233
Giraween Park
Graceville
225
Lindsay St
Hawthorne
206
Butterfield St
Herston
241
Bangalee Street
Jindalee
227
Kooringal Dr
Jindalee
228
Goodwin St
Kangaroo Point
211
Atkinson Dr
Karana Downs
232
Sellars St
Karana Downs
231
Tait St
Kelvin Grove
242
Castlemaine St
Milton
MILT 1-4
Willeen Ct
Mt Crosby
229
James St, Sydney St
New Farm
NF1-7
Waterloo St, Austin St
Newstead
239
Commercial Road, Stratton St
Newstead, Teneriffe
238
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5
BCC BPD Stage 2
Backflow Investigation - Summary Report
Streets
Suburb
System Number
Adina St, Frank St
Norman Park
210
Brentnall St
Norman Park
208
Waite St
Norman Park
209
Wendell St
Norman Park
207
Lang Parade
Rosalie
MR1
Tuckett Rd
Salisbury
224
Mollison St, Montague Road
South Brisbane West End
213
Douglas St
St Lucia
234
Gailey Road
St Lucia
235
Jerdanefield Rd
St Lucia
255
King Arthur Tce
Tennyson
253
Vivian St
Tennyson
223
Herbert St
Toowong
236
Dudley St
West End
219
Ferry Rd, Kurilpa St, Montague Rd, Drury St
West End
216
Montague Road
West End
214
Ryan St
West End
217
Ryan St
West End
218
Vulture St
West End
256
Ormadale Rd
Yeronga
249
Ormonde Rd
Yeronga
250
Ortive St
Yeronga
254
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BCC BPD Stage 2
Backflow Investigation - Summary Report
Figure 1
Map of systems for which installation of BPDs is feasible and 39 Stage 1 areas
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2.2
BCC BPD Stage 2
Backflow Investigation - Summary Report
7
Draft Backflow Management Strategy
For the drainage systems identified as feasible for installation of BPDs, the data for each system have been
collated to produce a draft backflow management strategy, centred on calculation of a ‘Relative Cost Benefit
Ratio’. High level probable construction costs were compared with benefits based on the damages potentially
mitigated by BPDs to produce the Relative Cost Benefit Ratio. The probable costs, potential benefits and the
Relative Cost Benefit Ratio are not designed to be highly detailed and a precise assessment, but rather a
reasonably accurate relative difference. While this ratio provides a guide to which systems provide the highest
relative value, a number of factors will be considered by Council when deciding a priority for installation of BPDs.
These factors may include cost benefit analysis, the number of properties impacted by floods, the cost of
installation, operational issues, previously programmed drainage network upgrades or critical infrastructure
impacted by flood.
High level estimates of probable construction costs for installation of BPDs were based on desktop data,
supported by site visits, and included consideration of the number and size of pipes requiring devices, the level of
construction required, such as chambers or new headwalls, and likely requirements for traffic management,
permits etc.
Design and construction management costs have not been included in these costs. No ongoing maintenance and
operational costs have been included in the costs, as it has been assumed that these costs will be similar for all
systems. Estimated installation costs have been calculated using installation costs of BPDs previously installed by
Council, as well as cost estimates from previous stages of this study. For the purposes of comparison, all costs
have been calculated in 2011 dollars, with the assumption that all construction costs will be paid in the first year of
construction. It is not intended that these estimated costs be used other than for a high level comparison between
systems.
Potential benefits of installing BPDs were calculated based on the number of properties flooded at a range of
flood levels and a widely used methodology calculating the potential value of damages to properties. Existing
data were used by Council to produce the damages projected for a number of different flood levels, covering only
direct flood damage (internal, external and structural damage) to residential, commercial, industrial and public
properties. Indirect damage (e.g. financial, clean-up and opportunity costs) and intangible damage (i.e. social
costs associated with flooding) is not included in the damage estimates. No data relating to the value of
properties are included as the methodology uses a set of average values. The flood damage values were used to
calculate the potential benefits of installing BPDs. These data are presented in Appendix C.
It should be noted that the ranking is indicative only and the actual construction schedule will need to consider
permit requirements, ease of access for construction and maintenance, as well as the availability of devices, etc.
other factors which may play a role include critical infrastructure, number of properties affected in the system,
strategic significance etc.
2.3
Review of a Range of BPDs
A review was carried out of literature available describing off-the-shelf BPDs, supplemented by consultation with
suppliers and with council staff to understand current practises, observed behaviour and previous history of BPD’s
under council control. Consideration was given to the different types of BPDs available and their possible
installation locations. Particular attention has been given to:
-
the head loss rating curve of the device (typically relating flow rate with head loss)
-
the ability to install the device simply and effectively
-
whether the device is best installed at an outlet or at some point further upstream
-
reducing required monitoring and maintenance of the device
-
the ability of the device to withstand high external pressures and high lateral velocities
-
suitability for installation in the intertidal zone
-
types of devices already installed within BCC
-
the procurement and installation cost of the device.
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8
BCC BPD Stage 2
Backflow Investigation - Summary Report
The aim of this review was to identify a number of types of BPD which could be installed in order to understand
their operating parameters. This data may be used to evaluate the effectiveness of installing different types of
BPDs in the networks with respect to introduced head loss which may lead to increased risk of flooding from local
storm inundation, as well as identify which BPDs would provide the highest efficiency and the lowest maintenance
requirements. This should be investigated further for each system at detailed design.
The results of the BPD review and evaluation are presented in the table included in Appendix A which includes
pictures of a number of a number of the BPDs reviewed and a summary shown in Table 2.
All devices will require assessment of the peak river height likely to be experienced by the device, in the form of
the hydraulic pressure the device can withstand.
The data collected in the BPD review are included in the design guidelines used at concept stage, which is
presented in Section 2.4.
Table 2
Device
Type
Summary of Review and Evaluation of Backflow Prevention Devices

Suitable installation
Notes
BCC experience
environment
Flap gates
A number of
options for
material,
hinges,
installation


Relative
head loss
Clearance below gate
required to reduce
likelihood of debris
preventing gate from
closing, resulting in
increased construction cost
in some cases.
Large sizes (above
1800mm) subject to higher
wear and tear due to
movement of flap gate
under normal river and tide
conditions
Poor experience with
fibre glass, steel and
single hinged. Better
results with aluminium,
double hinged.
Effective when well
designed.
Low
Duckbill
Vertical or
horizontal
opening

Able to cope with some
siltation in front of BPD so
less requirement for vertical
clearance below BPD.
Some problems with
debris preventing
duckbill from closing
High
Penstock
Vertical opening
via manual
control

Requires manual control
above gate
Must be manually activated
in flood situation and deactivated afterwards
Requires more regular
maintenance program to
ensure gate is operational
Not suitable where likely to
suffer siltation under gate.
Implications for high
maintenance
requirements need to be
taken into account
Zero



Inline
rubber flap
Insert fitted with
rubber flap to
provide one
way flow


Does not protrude from pipe
May be suited to installation
into existing manholes
No information provided.
Medium
Self
regulating
tide gate
Gate has
device fitted
with flotation
bulbs attached

Easily subject to damage,
so requires vandal free
environment
No information provided.
Unknown
Inflatable
rubber dam
Dam is inflated
in place when
required

Able to dam large open
outfalls
Must be manually activated
in flood situation and deactivated afterwards.
No information provided.
Zero
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
AECOM
Device
Type
2.4
9
BCC BPD Stage 2
Backflow Investigation - Summary Report
Notes

Suitable installation
environment

Easily subject to damage,
so requires vandal free
environment
BCC experience
Relative
head loss
Summary of Design guidelines
The choice of valve and location is subject to a number constraints that can be conflicting. Often there is not a
single clear choice, but a number of choices with conflicting advantages and disadvantages, resulting in different
costs and risks. Detailed consultation with appropriate, nominated Council officers has taken place to identify
previous experience and future preferences. Council will need to decide whether the proposed concept layouts
meet its needs.
The following considerations have been applied to develop the concept designs for the installation of BPDs, not
necessarily in any order:
-
Head loss impact on upstream flooding in local storm events must be minimised
-
BPDs fitted to outlets are generally cheaper to install due to reduced construction works
-
BPDs only to be fitted to outlets where access for maintenance is feasible within Council’s existing
maintenance resources. Generally this would require vehicular and personnel access to the outlet without
additional equipment.
-
Where access to outlets is not suitable, BPDs should be fitted in chambers constructed at an appropriate
location.
-
Selection of chamber locations should consider:

Access to chamber for maintenance with minimum of traffic management, i.e. off roads etc.

Suitable for excavation and construction of the chamber

At a suitable point on the network to be effective
-
Flap gates generally have lower head loss impact than duck bills, while inline valves are in between.
Penstocks have zero head loss impact as they are fully open when not activated.
-
Duck bills are considered to be more suitable where there is a likelihood of silt, sand or sediment deposition
-
Inline valves are suitable where construction work at the outlet is difficult or where a valve on the outlet
would be aesthetically inappropriate.
-
Flap gates larger than 1800 mm will be subject to higher wear and tear due to movement of flap gate under
normal river and tide conditions, but may be necessary in some situations, for instance where the head loss
impacts prevent use of a duckbill or penstocks are not appropriate.
-
The mass of the device should be considered during detailed design, including assessing the suitability of
the existing structure to anchor the device.
-
Flap gates generally should have minimum 150mm clearance between the invert of the pipe and the surface
of the apron to allow debris to fall out.
-
The visual impact of the devices has been considered, but it is recommended that alternative designs from
suppliers be considered where the visual impact is a critical factor
-
Environmental impacts of particular valves, and construction requirements should be considered at detail
design stage.
In general, flap gates installed on the outlet are the preference, due to low construction cost, ease of
maintenance, and reliable operation in Council experience. Chambers are chosen when access to the outlet for
construction or maintenance is difficult. Inline valves are chosen in order to avoid construction work at the outlet.
Duck bills are chosen where siltation is an issue. Penstocks are chosen where zero head loss is necessary, or for
very large outlets (e.g. over 2400mm), but the requirements for increased maintenance, activation and deactivation must be considered.
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3.0
BCC BPD Stage 2
Backflow Investigation - Summary Report
10
Concept Report – Case Study Areas Detailed Design
Three case study areas were identified at Stage 1, and the Concept Report into the Case Study Areas was the
first stage of the detailed design process for these areas. Following a review of the eight drainage systems
contained within the case study areas, two drainage systems were identified as likely to be suitable for initial
installation of BPDs.
The first stage of the investigations into the case study areas started with an examination of spatial data provided
by Council, particularly the relationship between outfalls considered likely to have contributed to backflow
inundation, their associated levees and statistical flood levels. Site visits were also conducted to outfalls publicly
accessible from dry land. Investigations were conducted into constructability constraints (plant access, condition
of existing structures, etc.) for each of the systems, as well as high level, desktop evaluation of statutory and
regulatory approval requirements for the selected study areas.
Table 3 gives a summary of the outcomes of the investigation for the eight systems in the case study areas, and
maps of these systems are presented in Appendix A.
From this data the New Farm C: Moray Street and Milton B: Cribb Street were identified as suitable for initial
installation of BPDs.
For these two systems, hydrological and hydraulic modelling was carried out to evaluate the impacts of installing
BPDs on the probability of flooding within the catchments of the systems. This modelling indicated that the impact
on flooding inside the catchment from local storm events was unlikely to be significant. Modelling also indicated
that flap gates have a smaller impact than duckbills. Concept layouts and cost estimates were developed for
these two drainage systems.
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Table 3:
BCC BPD Stage 2
Backflow Investigation - Summary Report
11
Summary of Outcomes of Investigations
System
Notes
Recommendation
New Farm A:
James St: NF1
and 2
-
Gully inlets on river side of levee
reduce effectiveness of BPDs on
outfalls
Potential permit issues
Unknown condition of older pipe,
requirement for large chamber to
accommodate large diameter pipes,
and constant tidal inundation make
construction of chamber complex
Develop preliminary design for chamber on
Merthyr Road in Stage 2
NF 3 possibly not connected to
system, or has the potential to be
disconnected from system eliminating
need for 1 BPD
NF4 and 5 already fitted with BPDs
NF6 and 7 outfalls have potential
permit issues. BPDs could be fitted in
chamber in New Farm Park.
Potential issues with groundwater
infiltration
Develop preliminary designs for BPDs in
Stage 2
NF 10 outfall not able to located
All outfalls in this location have
potential permit issues.
Possible to fit BPDs to pipe internal
diameter at each outfall.
Relatively small diameter pipes allow
for BPDs in manholes in Merthyr Park.
Progress to preliminary design for BPDs to
outfalls where modelling results are
appropriate, and siltation is manageable, or
manholes in Merthyr Park if necessary
-
New Farm B:
Sydney St: NF3-7
-
-
New Farm C:
Moray St: NF8-11
-
CBD
-
CBD1-3 not located
CBD4 suitable for fitting of BPD
Complicated work site, potential permit
issues
Develop preliminary designs for BPDs in
Stage 2
Milton A:
Castlemaine St:
MILT 1-4, 2A
-
Outfalls suitable for installation but
would require crib wall or cofferdam in
river for construction that require
permits
Possibility of chamber upstream, but
needs more detailed investigations
Develop preliminary designs for BPDs in
Stage 2
Possible to fit BPDs to pipe internal
diameter at each outfall, but there are
potential permit issues
Relatively small diameter pipes allow
for construction of manhole BPD
systems on Bicentennial Bikeway.
potential permit issues
Progress to preliminary design for BPDs to
outfalls where modelling results are
appropriate, and siltation is manageable, or
manholes in Bicentennial Bikeway if
necessary.
Milton Drain – large trapezoidal
channel, flood gates possible but major
engineering project.
Upstream solutions ineffective due to
open channel
Progress to concept design in Stage 2
Outfalls suitable for BPDs but permit
issues
Upstream chambers possible
Further risk assessment required in Stage 2
Milton B: Cribb St:
MILT 5-8
-
-
Auchenflower /
Toowong A: Lang
Parade: MR1
-
Auchenflower A:
Coronation Drive:
AUCH 1-3
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System
BCC BPD Stage 2
Backflow Investigation - Summary Report
Notes
-
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Levee (5m) only protects to Q50
(4.4m) not Q100 (5.4m) or 2011 (6.5m)
so BPDs provide protection up to Q50
Recommendation
12
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BCC BPD Stage 2
Backflow Investigation - Summary Report
13
Preliminary Design – New Farm C and Milton B
4.0
The preliminary design phase further developed the detailed design of the two drainage systems identified as
suitable for initial installation of BPDs.
The preliminary design stage built upon the investigations carried out in the concept stage. Further hydraulic
modelling was carried out to assess the impacts of the devices chosen on local storms within the catchment of the
drainage systems. Design development included further site visits, and consultation with suppliers and Council.
Documentation including a Works Specification, Schedule of Works, Standard Notes and details Drawings were
produced.
Detailed Design Report – New Farm C and Milton B
5.0
The detailed design stage finalised the design of the BPDs for installation in the two drainage systems in the case
study areas identified as suitable for initial installation of BPDs in the concept stage.
Detailed design documentation was produced including drawings for construction, erosion and sediment control
measures, final cost estimates, specifications, maintenance schedules and design report.
Concept Report – Remaining Systems in the Case Study
Areas
6.0
The Concept Report for the remaining systems in the case study areas built upon the previous work carried out as
part of the Detail Design of Stormwater Backflow Devices Project, but focused on the remaining six systems
within the three case study areas. In addition to the data collected during earlier investigations, a number of site
visits were undertaken, including on-site consultation with suppliers and Council officers.
Table 3 gives a summary of the outcomes of the investigation for the eight systems in the case study areas.
For these systems, hydrological and hydraulic modelling was carried out to evaluate the impacts of installing
BPDs on the probability of flooding within the catchments of the systems. The modelling showed that:
-
It is feasible to install either flap valves or duck bills to systems CBD1-4 & MR1 with minimal increase in
peak water levels (less than 50mm rise) during a local storm event.
-
For systems NF1-2, NF4-7, MLT1-4 & AUCH1-3, installation of either flap valves or duck bills has a
significant impact on peak water levels during a local storm event.
-
The higher tail water elevation generally results in a greater increase in water levels than the lower tailwater
elevation.
Locations were proposed for installation of appropriate BPDs for each system and these are presented in Table 4.
Concept layouts and cost estimates were developed for these two drainage systems. A high level, desktop
evaluation of statutory and regulatory approval requirements for the selected study areas was carried out. The
exact alignments and pipe sizes, as well as location of other services will need to be confirmed at detailed design
stage.
Table 4
Summary of Outcomes of Investigations
System
Recommendation
New Farm A: James St:
NF1 and 2
-
Installation of penstocks fitted to headwalls of outfalls.
New Farm B: Sydney St:
NF3-7
-
NF3 be disconnected from the system, following on-site investigations
Penstocks be fitted to the headwalls of outfalls NF6 and MF7
CBD
-
Installation of penstocks in chambers on CBD1, 2 and 3
Installation of flap gate on the outlet of CBD4
Milton A: Castlemaine St:
-
Installation of penstocks to the headwalls of the outfalls of MILT 1, 2, 2A and 3.
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Backflow Investigation - Summary Report
14
System
Recommendation
MILT 1-4, 2A
-
Installation of flap gates to the headwalls of the outfalls of MILT 4 and 5.
Auchenflower / Toowong
A: Lang Parade: MR1
-
Installation of a number of flap valves to a structure constructed across the
outlet of Milton Drain to manage backflow to the level of the pedestrian
walkway.
Installation of a system of penstocks to provide protection from backflow above
the level of the flap valve structure, including a penstock device to close off the
pedestrian walkway during a flood event.
-
Auchenflower A:
Coronation Drive: AUCH
1-3
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-
Installation of penstocks to the headwalls of the outfalls of AUCH 1-3
AECOM
7.0
BCC BPD Stage 2
Backflow Investigation - Summary Report
List of Abbreviations
Abbreviation
Meaning
ARI
Average Recurrence Interval
AUCH1-3
Auchenflower Drainage Outlets 1-3
BCC
Brisbane City Council
BPD
Backflow Prevention Device
CBD
(Brisbane) Central Business District
CBD1-4
Central Business District Drainage Outlets 1-4
DBYD
Dial Before You Dig
DEEDI
Department of Employment, Economic Development
and Innovation
DERM
Department of Environmental Resource Management
FRRB
Independent Flood Response Review Board
HAT
Highest Astronomical Tide
IDAS
Integrated Development Assessment System
m
metres
m, AHD
metres, Australian Height Datum
MHWS
Mean High Water Springs
MILT1-8
Milton Drainage Outlets 1-8
MR1
Milton Rosalie Trapezoidal Open Channel Outlet
MSL
Mean Sea Level
MWA
Max Winders Associates
NALL
Natural Assets Local Law
NF1-11
New Farm Drainage Outlets 1-11
PTW
Prescribed Tidal Works
Q100
Interchangeable with 100 year ARI flood
RCBC
Reinforced Concrete Box Culvert
RCP
Reinforced Concrete Pipe
WWBW
Waterway Barrier Works
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15
AECOM
BCC BPD Stage 2
Backflow Investigation - Summary Report
Appendix A
BPD Review Summary
and Images
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Appendix A
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BCC BPD Stage 2
Backflow Investigation - Summary Report
BPD Review Summary and Images
a-1
AECOM
BCC BPD Stage 2
Backflow Investigation - Summary Report
Appendix B
Case Study Area Location
Maps
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Appendix B
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BCC BPD Stage 2
Backflow Investigation - Summary Report
Case Study Area Location Maps
b-1
AECOM
BCC BPD Stage 2
Backflow Investigation - Summary Report
Appendix C
List of Systems for which
Installation of BPDs is
Feasible.
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Appendix C
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BCC BPD Stage 2
Backflow Investigation - Summary Report
List of Systems for which Installation of BPDs is
Feasible.
c-1
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BCC BPD Stage 2
Backflow Investigation - Summary Report
Appendix D
Maps of Systems
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Appendix D
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Backflow Investigation - Summary Report
Maps of Systems
d-1
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BCC BPD Stage 2
Backflow Investigation - Summary Report
Appendix E
Systems Assessed but
Excluded
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Appendix E
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Backflow Investigation - Summary Report
Systems assessed but excluded
e-1
AECOM
e-2
BCC BPD Stage 2
Backflow Investigation - Summary Report
Systems where flooding occurred but the river or creek was able to flood the
land directly
Streets
Suburb
Bogan St, Elliott St, Immarna St
Albion
Burrows St
Albion
Berkin Street
Bellbowrie
Taylor Street
Bulimba
Stanley Tce
East Brisbane
Plumridge St
Chelmer
Moorfields St
Fig Tree Pocket
Graceville Ave
Graceville
Lambert Road
Indooroopilly
Meiers Road
Indooroopilly
Witton Road
Indooroopilly
Capitol Drive
Jindalee
Curragundi Rd
Jindalee
Kilkivan ave
Kenmore
Lytton Road, Riverside Place
Morningside, Murrarie
Tekapo Street
Mount Omaney
Allawah Rd
Mt Crosby
Pinjarra Road
Pinjarra
Riversleigh Road
Pinjarra Hills
Esker St
Pinkenba
Lyndora Place
River Hills
Brinley Park
Seventeen Mile Rocks
Brisbane St; Warren St
St Lucia
Sandford Street; Glenolive Lane
St Lucia
Indooroopilly rd
Indooroopilly
Orleigh St
West End
Baikal Place
West Lake
Noble St
Wilston
Blackmore St
Windsor
Bowen St (east half)
Windsor
Bowen St (west half)
Windsor
Cullen St, Nicholas St, Victoria St, Northey St
Windsor
Eversley Tce
Yeronga
Systems where there was no Council pipe network evident in flooded system
Streets
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e-3
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Backflow Investigation - Summary Report
Systems where flooding occurred but the river or creek was able to flood the
land directly
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Streets
Suburb
Main St
Kangaroo Point