BORNHORST + WARD CONSULTING ENGINEERS SITE BASED STORMWATER MANAGEMENT PLAN FOR THE PROPOSED MULTI-TOWER RESIDENTIAL DEVELOPMENT LOCATED ON THE CORNER OF HIGH STREET AND SHERWOOD ROAD, TOOWONG PREPARED FOR STOCKLAND DEVELOPMENT PTY LTD OCTOBER 2016 Received BCC DA 20/10/2016 Stormwater drainage quantity sections are not part of this approved document. Stormwater quantity components are to be generally in accordance with the approved concept Site Services Plan drawing SK-0001 Rev A (amended in red 03/11/2017). Final details are to be finalised at the detailed design stage. AMENDED IN RED 03/11/2017 PLANS AND DOCUMENTS referred to in the APPROVAL Dated: 15/12/2017 PLANS AND DOCUMENTS referred to in the NEGOTIATED DECISION Dated: 16/3/2018
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BORNHORST + WARD CONSULTING ENGINEERS
SITE BASED STORMWATER MANAGEMENT PLAN
FOR THE PROPOSED
MULTI-TOWER RESIDENTIAL DEVELOPMENT
LOCATED ON THE CORNER OF
HIGH STREET AND SHERWOOD ROAD, TOOWONG
PREPARED FOR
STOCKLAND DEVELOPMENT PTY LTD
OCTOBER 2016
Received
BCC DA
20/10/2016
Stormwater drainage quantity sections are not part of thisapproved document. Stormwater quantity components are to begenerally in accordance with the approved concept Site ServicesPlan drawing SK-0001 Rev A (amended in red 03/11/2017). Finaldetails are to be finalised at the detailed design stage.
3. DEVELOPMENT PROPOSAL .....................................................................................................................................3
3.1 PROPOSED DEVELOPMENT .................................................................................................................................3
4.1.1 Rainfall Data .......................................................................................................................................................4
5.1 POLLUTANTS OF CONCERN .................................................................................................................................6
5.2.1 Meteorological Data ..........................................................................................................................................6
6. BRISBANE CITY COUNCIL CODES .............................................................................................................................8
Stormwater drainage quantity sections are not part of thisapproved document. Stormwater quantity components are to begenerally in accordance with the approved concept Site ServicesPlan drawing SK-0001 Rev A (amended in red 03/11/2017). Finaldetails are to be finalised at the detailed design stage.
BORNHORST + WARD | HIGH STREET AND SHERWOOD ROAD, TOOWONG
LIST OF FIGURES
Figure 1: Locality Plan ............................................................................................................................................................1
Table 1: Pre and Post Development Peak Stormwater Discharge .........................................................................................5
Table 2: South East Queensland Water Quality Objectives ...................................................................................................6
Appendix C Existing Stormwater and Contour Information
Appendix D Rational Method Calculations
Appendix E Stormwater Treatment Information
Appendix F Brisbane City Council Codes
Stormwater drainage quantity sections are not part of this
approved document. Stormwater quantity components are to begenerally in accordance with the approved concept Site ServicesPlan drawing SK-0001 Rev A (amended in red 03/11/2017). Finaldetails are to be finalised at the detailed design stage.
BORNHORST + WARD | HIGH STREET AND SHERWOOD ROAD, TOOWONG
The proposal is for three multi-storey towers developed over a single lot. The development will include
approximately 530 apartments, some retail tenancies and basement car parking. Development will be
completed in three stages with a total development area of 8980m2. See Appendix A for more details.
3.2 PROPOSED STORMWATER DRAINAGE
Post development, all stormwater connections currently servicing the site will be made redundant and removed.
It is proposed to construct a new stormwater line within Sherwood Road to facilitate the stormwater treatment
device and stormwater diversion (see the Site Services Plan in Appendix B). This line will be constructed from
the existing stormwater chamber on the opposite side of Sherwood Road with downstream infrastructure
designed to convey the Q50 event from the upstream catchment. Therefore roof and allotment drainage for the
site is to be level IV drainage capable of conveying the 2% AEP (50yr) storm event with no surcharge structures
required. This will improve current overland flow flooding conditions within the Sherwood Road road reserve as
the Q50 event is already conveyed underground. Requirements for internal drainage will be confirmed via a
hydraulic analysis by a hydraulic engineer in the detailed design phase. Refer to the Site Services Plan in Appendix
B for more information.
As mentioned previously, constructing a new stormwater line from the stormwater chamber on the opposite
side of Sherwood Road will aid in providing the required depth to allow the site to facilitate stormwater
treatment and the 88 Jephson Street diversion. Stormwater chambers directly adjacent to the site are quite
shallow and therefore do not provide enough depth to discharge flows. Refer to the Bornhorst and Ward
Stormwater Management Plan for more information on stormwater quality and quantity requirements.
The external catchment from 88 Jephson Street will need to be catered for post development. It is proposed
that this diversion is facilitated within basement 01 and discharge to Sherwood Road as per existing conditions.
The roof water diversion will be a 450mm diameter FRC pipe that will cross the loading dock and continue
through the wall cavity in the basement level as shown in the preliminary Site Services Plan in Appendix B of this
report. The line will be accessible via access doors at regular intervals.
Stormwater drainage quantity sections are not part of thisapproved document. Stormwater quantity components are to begenerally in accordance with the approved concept Site ServicesPlan drawing SK-0001 Rev A (amended in red 03/11/2017). Finaldetails are to be finalised at the detailed design stage.
BORNHORST + WARD | HIGH STREET AND SHERWOOD ROAD, TOOWONG
Under the Brisbane City Council guidelines, several design elements were identified in relation to stormwater
management issues. Brisbane City Council must be satisfied that:
• The proposed development can be drained;
• The stormwater management system can follow the features and functions of the natural drainage
system;
• The volume, timing, velocity and pollutant load of stormwater has no adverse effect on any
surrounding properties or receiving waters; and
• Suitable provision is made in the design layout to accommodate for major drainage.
Stormwater discharge requirements for the site will comply with Brisbane City Council's Stormwater
Management Code.
4.1 PEAK FLOW CALCULATIONS
Modelling of stormwater runoff quantity has been considered for the existing site conditions and operational
phase of the development. The Rational Method as outlined in QUDM was used to determine the peak flow rate
corresponding to the minor and major storm events for this development.
Brisbane City Council Infrastructure Planning Scheme Policy, Chapter 7, Table 7.2.2.3.B, “Design Standards for
Drainage Systems” was used to identify the design storm events for this development as:
Minor (Major Drainage System) - 10% AEP (1 in 10 year ARI)
Major (Minor Drainage System) - 2% AEP (1 in 50 year ARI)
Major (Overland Flow) - 1% AEP (1 in 100 year ARI)
Flow rates for the developed site have been evaluated as a total discharge from the site.
4.1.1 Rainfall Data
The IFD data used in the Rational Method calculations was obtained from the Australian Bureau of Meteorology
website based on the approximate latitude and longitude of the development site (LAT: 27.47oS, LONG: 153.
03oE). This data indicated the 60 minute, 10 year ARI rainfall intensity applicable to the development site is
71mm/hr. This rainfall intensity was used in conjunction with the fraction impervious values to determine the
coefficients of runoff for the existing and developed phases of the development in accordance with QUDM.
4.1.2 Peak Flow Discharge
Table 1 is a summary of the existing and proposed peak site stormwater discharges for varying storm events.
Peak flows were calculated in accordance with the Rational Method as outlined in the Queensland Urban
Drainage Manual. Detailed calculations are attached in Appendix D for reference and review.
The coefficient of runoff was taken to be 0.9 and 0.86 for the existing and proposed scenarios respectively. For
the existing and proposed site, this was determined from existing and proposed impervious areas shown on
aerial photography and site plans. The time of concentration for both cases was determined in accordance with
QUDM. The existing and proposed time of concentration was calculated at 5 minutes based on Table 4.6.3 of
QUDM.
Stormwater drainage quantity sections are not part of thisapproved document. Stormwater quantity components are to begenerally in accordance with the approved concept Site ServicesPlan drawing SK-0001 Rev A (amended in red 03/11/2017). Finaldetails are to be finalised at the detailed design stage.
BORNHORST + WARD | HIGH STREET AND SHERWOOD ROAD, TOOWONG
Table 1: Pre and Post Development Peak Stormwater Discharge
Ca
tch
me
nt
De
tail
s
Parameter Existing Developed Difference
Area (ha) 0.898 0.898 0
Coefficient of Runoff (C10) 0.9 0.86 0
Time of Concentration (min) 5 5 0
10 year Rainfall Intensity (mm/hr) 215 215 0
50 year Rainfall Intensity (mm/hr) 292 292 0
100 year Rainfall Intensity (mm/hr) 327 327 0
Dis
cha
rge
100% AEP (m3/s) 0.815 0.815 0
50% AEP (m3/s) 0.729 0.721 -0.008
10% AEP (m3/s) 0.482 0.461 -0.021
As indicated in the table above, the peak discharge from the development will be decreased for all storm events
as a result of the decrease in impervious surfaces. Therefore, no stormwater mitigation measures are proposed
for the development. This is consistent with Section 7.5.5 of Brisbane City Council 2014 City Plan which states
that “sites with greater than 60% existing sealed impervious surfaces will generally not require stormwater
detention because there is little change in peak flow”.
5. STORMWATER QUALITY
The following extract from the document describes when a development is considered high risk, under Table
9.4.9.3.A of the BCC City Plan 2014:
a) A material change of use for an urban purposes which involves greater than 2500m2 of land that:
i. Will result in an impervious area greater than 25% of the net developable area, or
ii. Will result in 6 or more dwellings.
b) Reconfiguring a lot for urban purposes that involves greater than 2500m2 of land and will result in 6 or
more lots;
c) Operational works for an urban purpose which involves disturbing greater than 2500m2 of land.
As the proposed development involves operational works disturbing a land area greater than 2500m2, the city
plan requirements for water quality are applicable to the proposed development. As such the development will
be modelled in MUSIC.
Stormwater drainage quantity sections are not part of thisapproved document. Stormwater quantity components are to begenerally in accordance with the approved concept Site ServicesPlan drawing SK-0001 Rev A (amended in red 03/11/2017). Finaldetails are to be finalised at the detailed design stage.
BORNHORST + WARD | HIGH STREET AND SHERWOOD ROAD, TOOWONG
The SPEL treatment device will require periodic maintenance to ensure it can continue to function efficiently.
SPEL products will require monitoring every six months as per the attached maintenance information in
Appendix E. System maintenance will be via the maintenance access hole on the ground floor. Maintenance can
be provided by using either a mobile vacuum cleaner or vacuum truck operated by a SPEL Environmental certified
maintenance contractor.
6. BRISBANE CITY COUNCIL CODES
The relevant Brisbane City Council Codes with respect to engineering aspects have been addressed. These codes
will assist in assessing operational works requirements. The codes addressed in this report include:-
• Stormwater Management Code
The completed codes can be found attached in Appendix F of this Report.
7. SUMMARY
This Stormwater Management Plan has demonstrated that the proposed development located on the corner of
High Street and Sherwood Road, can be developed in accordance with Engineering Best Management Practice,
Brisbane City Council guidelines and the State Planning Policy 2014. The following points summarise the findings
and recommendations:
• There are no flood levels or flags for building or development purposes exist for the development site
and therefore it is expected that the site is at a low risk of flood inundation;
• It is proposed that stormwater is discharged to the stormwater infrastructure within Sherwood Road
road reserve as per existing conditions;
• A new stormwater line is proposed within Sherwood Road to service the site. This line will be
constructed from the stormwater chamber on the northern side of the Sherwood Road road reserve.
Existing stormwater connections and infrastructure servicing the site will be made redundant;
• The existing stormwater connection for 88 Jephson Street is currently provided through the
development areas internal drainage system. Post development, it is proposed to divert this roof water
connection within the basement level;
• There will be no increase in peak stormwater runoff as a result of the development, therefore
detention will not be required;
• Stormwater runoff is to be treated by an underground propriety device before being directed to the
stormwater infrastructure within the Sherwood Road road reserve to the north of the site.
Stormwater drainage quantity sections are not part of thisapproved document. Stormwater quantity components are to begenerally in accordance with the approved concept Site ServicesPlan drawing SK-0001 Rev A (amended in red 03/11/2017). Finaldetails are to be finalised at the detailed design stage.
BORNHORST + WARD | HIGH STREET AND SHERWOOD ROAD, TOOWONG
The SPELFilter system requires periodic maintenance to continue operating at the design efficiency. Themaintenance process comprises the removal and replacement of each SPELFilter cartridge and the cleaning of thevault or manhole with a mobile vacuum cleaner. A sucker truck can also be an option however wet/dry mobile vacuum cleaner is a more cost effective solution which achieves the maintenance requirements. SPELFilter maintenance should be performed by a SPEL Environmental certified maintenance contractor.
The maintenance cycle of the SPELFilter system will be driven mostly by the actual solids load on the filter. Thesystem should be periodically monitored to be certain it is operating correctly. Since stormwater solids loads can bevariable, it is possible that the maintenance cycle could be more or less than the projectedduration.
The SPELFilter systems in New Development applications are designed to treat the WQv in 24 hours initially. Laterin the cycle these cartridges will flow at a slower rate, and when the WQv does not drain down within +/- 40 hoursafter the storm event, the system must be maintained.
When a SPELFilter system is first installed, it is recommended that it be inspected every six (6) months. When thefilter system exhibits flows below design levels the system should be maintained. Filter cartridge replacement shouldalso be considered when sediment levels are at or above the level of the 4 inch manifold system. Please contactSPEL Environmental for maintenance cycle estimations or assistance at 13 SPEL.
MAINTENANCECHAPTER
4
Received
BCC DA
20/10/2016
21
1. Remove the manhole covers and open all access hatches.2. Before entering the system make sure the air is safe per OSHA Standards or use a breathing apparatus. Use low
O2, high CO, or other applicable warning devices per regulatory requirements.3. Using a mobile wet/dry vacuum cleaner or a sucker truck to remove sediments that can be removed prior to entry.4. Using a small lift, remove the used cartridges by lifting them out.5. Any cartridges that cannot be readily lifted directly out of the vault should be removed from their location and
carried to the lifting point using the Trolley system installed in the Vault (if applicable).6. When all cartridges are removed, remove the balance of the solids and water; then loosen the stainless clamps
on the couplings in the pipe manifold; remove the drain pipes as well. Carefully cap the manifold and rinse the floor removing the balance of the collected solids.
7. Clean the manifold pipes, inspect, and reinstall.8. Install the exchange cartridges and close all covers.9. The used cartridges must be sent back to SPEL Environmental for exchange/recycling and credit on undamaged
units.
MAINTENANCE
BORNHORST + WARD | HIGH STREET AND SHERWOOD ROAD, TOOWONG