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Garnet Street RFI_20150513_ITC (Part 1)
Attached to the e-mail OPW15/0044 Response to Information Request Email 1 of 1.
13 May 2015 Noosa Council PO Box 141 TEWANTIN QLD 4565 Attention: Mark Lewis APPLICATION No. OPW15/0044 – ENGINEERING WORKS (GARNET STREET, COOROY) Lot 45 USL 31429, Lot 204 MCH 976, Lot 157 MCH 4833 RESPONSE TO INFORMATION REQUEST DATED 27 APRIL 2015 Reference is made to Council Request for Information dated 27 April 2015 regarding the Development Permit for Operational Works (Roadworks, Stormwater, Drainage, Landscaping, Clearing vegetation and Waterway Barrier Works) associated with the upgrade of Garnet Street, Cooroy. In response to the Information Request, please refer below for our response to each of the issues:- HYDRAULICS & WATER QUALITY Issue 1 The submitted documentation does not provide any details with respect to safety aspects of the proposed culverts. Information Required Provide a risk assessment undertaken by an RPEQ in accordance with Section 12 of QUDM assessing the proposed culverts and specifically considering inlet screens. If necessary, revised engineering drawings and calculations should be submitted to Council with the risk assessment. Response The proposed culverts have been assessed under the criteria in Section 12.04.01 of QUDM and based on locality have been classified as a Contact Class B location. In assessment of the inlet screen criteria within a Class B location, consideration has been given to pedestrian thoroughfare, fencing & road barriers, pipe size, travel time and the greater Cooroy Creek in terms of flow and accessibility. Assessment Criteria Comments Pedestrian Thoroughfare Pedestrian movements have been concentrated to the northern side of Garnet Street by the construction of formalised concrete footpath. Access and vehicle stopping is discouraged from the southern side (inlet side of the culverts) by a fully sealed shoulder, full length guard rail and barrier kerb.
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Page 2
Road Barriers Road barrier in the form of guard rail has been
proposed for the southern side of Garnet Street for
the full length of the upgrade works.
Pipe Size Pipe sizes consist of DN 2700mm, DN 2100mm and
2400mm x 1200mm RCBC and pose a minimal risk of
entrapment.
Travel Time For the DN 2700mm pipe arrangement, a length of
14.64m and pipe velocity of 1.38m/s (Hydrology and
Water Flood Report) have been used to calculate a
travel time of 10.6 seconds.
For the 2400mm x 1200mm RCBC arrangement, a
length of 15.00m and pipe velocity of 0.93m/s
(provided by Hydrology and Water) has been used
to calculate a travel time of 16.1 seconds. Whilst
this time is greater than an expected pipe full travel
time of 10 seconds, this set of culverts is elevated
above the base of Cooroy Creek and operates as a
secondary system during flooding.
For the skewed orientation of the DN2100 pipe
arrangement, a length of 69.34m and pipe velocity
of 1.83m/s (provided by Hydrology and Water) have
been used to calculate a travel time of 37.9 seconds.
Whilst this time is greater than an expected pipe full
travel time of 10 seconds, this set of culverts is
elevated above the base of Cooroy Creek and
operates as a secondary system during flooding.
Cooroy Creek – flow and accessibility Cooroy Creek has a history of conveying significant
flows from a large western catchment and regularly
flows full to the extent of overtopping Garnet
Street.
The culvert amplification works provide a balanced
solution whereby Garnet Street meets the safe
trafficable requirements without adversely
impacting on flood levels upstream and
downstream.
While the inundation levels across Garnet Street will
be reduced by the amplification works, the greater
Cooroy Creek will continue to flow at high levels at
regular intervals. On this basis, hazards and risk
associated with the culverts must be considered in
the context of the Cooroy Creek flow characteristics.
Furthermore, construction of inlet screens on the
culverts and potential blockage as a result of debris
collection may result in the balanced flow/flood
storage model being compromised and adverse
changes to flood levels in the greater area.
Page 3
A risk assessment has been completed on the travel times within the culverts in accordance with Chapter
12 of the Queensland Urban Drainage Manual (QUDM). The risk assessments are attached with this
document.
Assessment for the Requirement of Inlet Grates
Following a risk assessment of the pipe and culvert structures, it was determined that further evaluation
was required to determine whether inlet grates are required to be installed.
Reference is made to Section 12.04.3 of QUDM – Site conditions where barrier fencing or inlet/outlet
screens may not be appropriate. This section highlights that examples where inlet/outlet screens may not
be appropriate include:
i. Where the overall risk to human life as a result of the installation is judged to be greater than if the
device was not installed.
ii. Where there is an unacceptable risk of trapping wildlife (aquatic or terrestrial) or causing
disruption to an essential wildlife corridor.
iii. Where debris blockage of the fence or screen will cause or increase floor level flooding. The
degree of blockage must be comparable with the existing and likely future catchment conditions.
The installation of the grates has the potential to impact on all of the abovementioned items.
It can be argued that the installation of grates can result in a greater overall risk to human life whereby
someone could be pinned against the inlet grates during a storm event. Without the installation of inlet
grates, a person would be swept through the pipes/culverts and exit from the outlet. This is just one
example where the overall risk to human life is increased due to the inclusion of inlet grates.
The inclusion of inlet grates creates a serious potential for wildlife to be trapped. Similar to the example
offered above, it could be conceived that wildlife has the potential to be pinned or trapped against the
grates during storm events. Without the installation of inlet grates, this risk of being trapped is removed as
the wildlife would be swept through the pipes/culverts.
Inlet grates also have the potential of disrupting the wildlife corridor through issues associated with
blockage and the potential for debris to accumulate effectively isolating the southern and northern sides of
Garnet Street. The exclusion of inlet grates reduce the potential for this to occur as the size of the pipes
and culverts are large enough to not collect debris and maintain connectivity between the southern and
northern sides of Garnet Street.
The most important argument for excluding inlet grates is associated with the balance between achieving
non-worsening of flood inundation levels upstream and downstream of the Garnet Street crossing. Inlet
grates will produce increased blockages at the inlet to the pipes and culverts due to the collection of debris.
This will ultimately result in increased flood inundation levels to properties upstream of the culvert
crossing.
The location of the pipes and culverts has been identified as a low risk area due to it being located in a
semi-rural area with very little pedestrian traffic along Garnet Street. The footpaths are located on the
northern side of Garnet Street, reducing the volume of pedestrian traffic directly adjacent to the inlet of the
pipes and culverts. Guardrail has been included on the southern side of Garnet Street to further prevent
and deter entry to the inlet of the pipes and culverts.
Apart from the safety and performance issues identified above, maintenance requirements should also be
considered by Council. It is not unreasonable to suggest that the large size of the proposed culverts will be
primarily self-cleansing and installation of excessively large grates will require more regular maintenance
and potentially impact on performance. During a recent storm event onsite, a representative from SMEC
witnessed the event that involved the existing culverts flowing at full capacity. It was verbally reported that
the pipes did not suffer from blockage due to debris and it could be assumed that the inclusion of larger
pipes would also not impact from the collection of debris.
Page 4
Resultant Management Practices
Following the completion of the risk analysis and subsequent review of all culvert inlet structures, it has
been determined that the following management practices will be included:
• Signage erected along Garnet Street to alert people of the potential danger.
• Inclusion of guardrail along the southern edge of Garnet Street which will act to deter people from
entering this area.
• No footpaths to be located on the southern side of Garnet Street.
Based on the above, and in accordance with the attached Risk Evaluation spreadsheets, we consider that
inlets grates should not be installed.
Issue 2
Certification of the design from an RPEQ (Hydrologist) regarding flooding affects is required.
Information Required
Certification of the design from an RPEQ (Hydrologist) that states that, should the works be constructed in
accordance with the submitted plans, the works will:
a) Achieve compliance with the higher order conditions
b) Be in accordance with QUDM with specific reference to blockage factors, debris barriers, etc.
Response
A certification letter from Rob Stewart of Hydrology and Water addressing the abovementioned items is
attached with this correspondence (refer to Attachment 1).
Issue 3
The construction of the works will extend into the adjacent playing fields and will also potentially require closing
of Garnet Street for extended periods of time.
Information Required
Provide a preliminary Construction Management Plan that specifically addresses the following:
a) Traffic Management during all aspects of the construct phase including:
i) A Traffic Management Control Plan
ii) Any expected road closures including alternate routes and expected extent of closures
b) Works programme identifying key components of the works and their respective durations
c) Establishment of a communication protocol with the general public, adjoining owners, emergency
services and local businesses
d) Identification of complaint management procedures
e) Details on the location of external fill sites/sources, the haulage route, etc
f) Details the time frame and construction methods to be used for those works within the playing fields
Please note Council’s preference for timing of the works impacting on the field is to be:
• After 22 August to allow the soccer club to complete fixtures.
• Completed before the summer soccer season starts in mid-October.
• Kept to a minimum duration.
• Boundary clearance requirements around the field are 3m from the line marking. The applicant will
need to ensure that any works commenced prior to the end of season complies with the buffer
requirements.
• Impacts on the field integrity to be kept to a minimum and full reinstatement of the field to pre-works
conditions are completed by the developer.
Page 5
Please note in relation to the proposed continuation of the 4m high back of goal fencing to form a barrier to the western most drain, it is considered that the use of 1200mm fencing similar to the property fencing would be sufficient to secure the drain opening from the playing fields. It is noted that the 4m high fencing requires significant footings and bracing. Whilst Council has indicated their preference in regard to the fencing it is the design engineers (RPEQ) responsibility to prepare the final design of the necessary safety fencing. Response At this stage, a Contractor has not been appointed as the works are currently being tendered. The abovementioned conditions have been included in the tender documents and a Traffic Management/Construction Management Plan will be provided to Council once available. We request that Council issue a conditional Decision Notice that requires a Traffic Management/Construction Management Plan be provided to Council prior to a pre-start meeting being conducted. The extension of the existing fence along the southern edge of the sporting fields has been reduced to 2.0m. Issue 4 The state Planning Policy Appendix 3 has performance objectives for the management of water quality. It is not clear from the application whether these Policies are met – in particular in relation to how the culverts will change waterway hydrology and peak flows, and the impacts this will have on the creek geomorphology Information Required Demonstrate how the culverts have been designed to mitigate changes on the creeks hydrology and geomorphology. In particular, demonstrate compliance with Performance Outcome PO6 and PO7 of the SPP Code: Water Quality. Response Reference is made to the report titled “Garnet Street Culvert Upgrade Hydraulic Assessment” prepared by Hydrology and Water dated 29 July 2014. Section 5 of the report demonstrates and provides a discussion of the results in relation to the hydrology of the creek at the culvert location. The design has been undertaken in an effort to reduce the ongoing impacts of bank erosion associated with the flows through the existing culverts at this location. The inclusion of rock gabions and rock protection in the immediate vicinity of the inlet and outlet to the culverts will help mitigate further erosion in the area of the works. As part of the tender documents, the Contractor is required to submit a CPESC certified erosion and sediment control plan and the works undertaken in accordance with all relevant environmental legislation. A certified erosion and sediment control plan will be provided to Council prior to the commencement of the pre-start meeting. Issue 5 The Noosa Plan Sediment and Erosion Control Code require that Development minimises erosion and sediment transport and also that Stormwater is diverted around disturbed areas. The provided Erosion and Sediment Control plan does not clearly demonstrate that best practice sediment and erosion controls are proposed to achieve these outcomes. Information Required Demonstrate that the proposed strategy to manage sediment and erosion control is current best practice and therefore achieves the objective of minimisation of impacts. In particular, demonstrate how the proposed construction strategy for the culverts within the watercourse is consistent with the International Erosion and Sediment Control Association - Best Practice Erosion and Sediment Control Appendix I, Instream Works 2008.
Page 6
Response
As part of the tender documents, the Contractor is required to submit a CPESC certified erosion and sediment
control plan and the works undertaken in accordance with all relevant environmental legislation. A certified
erosion and sediment control plan will be provided to Council prior to the commencement of the pre-start
meeting.
Should you require any further information, please do not hesitate to contact the undersigned.
Regards,
Brad Downes
BE (Env) MIE Aust RPEQ (Civil) CPEng (Civil)
Urban Engineering Principal - Sunshine Coast
SMEC Australia Pty Ltd
Attachments
1. Certification letter from Rob Stewart
2. Risk Assessments
3. Garnet Street Drawing Set
Page 7
ATTACHMENT 1 – CERTIFICATION LETTER FROM ROB STEWART [OCR of page images] ATTACHMENT 1 — CERTIFICATION LETTER FROM ROB STEWART A~ ‘oon’, CONSULT AUSTRALIA SMEC Holdings Ltd ABN 84 057 274 049 SMEC Operations Pty Ltd ABN 68 085 474 428 . SMEC International Pty Ltd ABN 32 085 440 619 SMEC Australia Pty Ltd ABN 47 085 475 149 7 ‘nes | Engen | Desgn SMEC Services Pty Ltd ABN 79 086 504 792 cxceaertcoma?
Page 8
PO Box 120 Coolum Beach Qld 4573
Tel 07 5448 2839 Mob 0405 194 639
Email [email protected]
Web www.hydrologyandwater.com.au
ABN 25 153 466 981 ACN 153 466 981
12th May 2015 Our Reference: J00155Lt6
Noosa Council
c/o Brad Downes
SMEC Australia
By Email: [email protected]
Response to Information Request:
Garnet Street Operation Works Application OPW15/0044 – Hydrologist Certification (Item 2)
Dear Sir/Madam,
Rob Stewart of Hydrology and Water Management Consulting Pty Ltd (HWMC) hereby certifies that
works that are constructed in accordance with the submitted plans (attached for reference) will:
• Achieve compliance with the higher order conditions (in as far as they relate to Cooroy
Creek flood impacts and road immunity);
• Be in accordance with current industry guidelines, including QUDM and the latest Australian
Rainfall and Runoff guidelines. It is noted that all culverts have been modelled assuming a
blockage factor of 20% for the impact assessment and a copy of the 1% AEP and the 10%
AEP impact maps are attached. Modelling has also made allowance for blockage of the
proposed guard rails and traffic barriers.
Kind Regards,
Rob Stewart MIEAust CPEng
Director
RPEQ 13272
Enc: Operational Works Drawings
Impact Maps
Page 9
0 15 30 45 (m)
1:1500 (A3)
Legend
DCDB
Upgraded Culverts
Flow Velocity Vector
Impact
(m)
> 0.20
0.15 to 0.20
0.10 to 0.15
0.05 to 0.10
0.01 to 0.05
-0.05 to -0.01
-0.10 to -0.05
-0.15 to -0.10
-0.20 to -0.15
< -0.20
Was Dry, Now Wet
Was Wet, Now Dry
© Hydrology and Water Management Consulting Pty Ltd (HWMC) 2014.
HWMC endeavours to ensure that the information contained in this
figure is correct at the time of publication. Furthermore, HWMC
makes no representations, warranties or guarantees about its
accuracy, reliability, completeness or suitability for any
particular purpose.
Hydraulic Assessment of the
Garnet Street Culvert Upgrade
Peak Flood Level Impacts
10% AEP Design Event (DIS)
20% Culvert Blockage
(Case D07a Vs B02e)
Client: Peet Limited
C:\HWMC\Projects\J00155_Greenwood_Grove_Cooroy_Modelling\Calcs\MapInfo\Figures
Page 10
0 15 30 45 (m)
1:1500 (A3)
Legend
DCDB
Upgraded Culverts
Flow Velocity Vector
Impact
(m)
> 0.20
0.15 to 0.20
0.10 to 0.15
0.05 to 0.10
0.01 to 0.05
-0.05 to -0.01
-0.10 to -0.05
-0.15 to -0.10
-0.20 to -0.15
< -0.20
Was Dry, Now Wet
Was Wet, Now Dry
© Hydrology and Water Management Consulting Pty Ltd (HWMC) 2014.
HWMC endeavours to ensure that the information contained in this
figure is correct at the time of publication. Furthermore, HWMC
makes no representations, warranties or guarantees about its
accuracy, reliability, completeness or suitability for any
particular purpose.
Hydraulic Assessment of the
Garnet Street Culvert Upgrade
Peak Flood Level Impacts
1% AEP Design Event (DIS)
20% Culvert Blockage
(Case D07a Vs B02e)
Client: Peet Limited
C:\HWMC\Projects\J00155_Greenwood_Grove_Cooroy_Modelling\Calcs\MapInfo\Figures
Page 11
ATTACHMENT 2 – RISK ASSESSMENTS [OCR of page images] ATTACHMENT 2 — RISK ASSESSMENTS CONSULT AUSTRALIA SMEC Holdings Ltd ABN 84 057 274 049 SMEC Operations Pty Ltd ABN 68 085 474 428 SMEC International Pty Ltd ABN 32 085 440 619 SMEC Australia Pty Ltd ABN 47 085 475 149 ‘nes | Engen | Desgn SMEC Services Pty Ltd ABN 79 086 504 792
Page 12
Risk Register - 2400mm x 1200mm RCBC
Existing Controls of Effectiveness
Is the Risk
Identified Risk/Hazard Controls in Place Identified of Existing Likelihood of Event Consequence Risk Rating Outcome
Significant?
Risk/Hazard Controls
All culverts and stormwater inlets with a minimum inlet dimension greater than Fencing and road barrier, large pipes Further asessment
Yes Good 2 3 High No
375mm, and an expected pipe-full flow travel time greater than 10 seconds. (DN2100), located on a watercourse, required
All culverts and stormwater inlets with a minimum inlet dimension greater than See Below for See Below for
Not applicable Please Select… Please Select… #N/A #N/A #N/A
375mm and a conduit containing a potential impact structure. Categories… Categories…
All culverts and stormwater inlets with a minimum inlet dimnesion greater than
See Below for See Below for
375mm that discharge to waters that are either inaccessible to a potential rescuer, Not applicable Please Select… Please Select… #N/A #N/A #N/A
Categories… Categories…
or have no suitable egress.
All culverts or stormwater inlets where the assessed safety risk is considered See Below for See Below for
Not applicable Please Select… Please Select… #N/A #N/A #N/A
unacceptable. Categories… Categories…
See Below for See Below for
Not applicable Please Select… Please Select… #N/A #N/A #N/A
Categories… Categories…
Likelihood Table Consequence Table
Level Descriptor Description Level Descriptor Description
The event will occur
1 Almost Certain 5 Major Fatal injuries
on an annual basis
Travel Time Calculation
Distance = 15.00m, pipe velocity = 0.93m/s, travel Time = 16.1s (>10s)
The event has
occurred several Permanent injury or
2 Likely 4 Significant
times in recorded psychological trauma
history
The event is likely to
Broken bone or open
3 Possible occur once in 50 3 Moderate
flesh wound
years
The event has
4 Unlikely occurred once 2 Minor Cuts and bruises
before
The event has not
occurred locally, but Wet clothes or mild
5 Rare 1 Very Minor
has occurred scare or mild trauma
elsewhere
Consequence
Likelihood 1 2 3 4 5
1 Medium High High Very High Very High
2 Medium Medium High High Very High
3 Low Medium High High High
4 Low Low Medium Medium High
5 Low Low Medium Medium High
Page 13
Risk Register - 2100mm RCP
Existing Controls of Effectiveness
Likelihood of Death Is the Risk
Identified Risk/Hazard Controls in Place Identified of Existing Consequence Risk Rating Outcome
or Injury Significant?
Risk/Hazard Controls
All culverts and stormwater inlets with a minimum inlet dimension greater than Fencing and road barrier, large pipes Further asessment
Yes Good 2 4 High No
375mm, and an expected pipe-full flow travel time greater than 10 seconds. (DN2100), located on a watercourse, required
All culverts and stormwater inlets with a minimum inlet dimension greater than See Below for See Below for
Not applicable Please Select… Please Select… #N/A #N/A #N/A
375mm and a conduit containing a potential impact structure. Categories… Categories…
All culverts and stormwater inlets with a minimum inlet dimnesion greater than
See Below for See Below for
375mm that discharge to waters that are either inaccessible to a potential rescuer, Not applicable Please Select… Please Select… #N/A #N/A #N/A
Categories… Categories…
or have no suitable egress.
All culverts or stormwater inlets where the assessed safety risk is considered See Below for See Below for
Not applicable Please Select… Please Select… #N/A #N/A #N/A
unacceptable. Categories… Categories…
See Below for See Below for
Not applicable Please Select… Please Select… #N/A #N/A #N/A
Categories… Categories…
Likelihood Table Consequence Table
Level Descriptor Description Level Descriptor Description
The event will occur
1 Almost Certain 5 Major Fatal injuries
on an annual basis
Travel Time Calculation
Distance = 69.34m, pipe velocity = 1.83m/s, travel Time = 37.9s (>10s)
The event has
occurred several Permanent injury or
2 Likely 4 Significant
times in recorded psychological trauma
history
The event is likely to
Broken bone or open
3 Possible occur once in 50 3 Moderate
flesh wound
years
The event has
4 Unlikely occurred once 2 Minor Cuts and bruises
before
The event has not
occurred locally, but Wet clothes or mild
5 Rare 1 Very Minor
has occurred scare or mild trauma
elsewhere
Consequence
Likelihood 1 2 3 4 5
1 Medium High High Very High Very High
2 Medium Medium High High Very High
3 Low Medium High High High
4 Low Low Medium Medium High
5 Low Low Medium Medium High
Page 14
Risk Register - 2700mm RCP
Existing Controls of
Effectiveness of Is the Risk
Identified Risk/Hazard Controls in Place Identified Likelihood of Event Consequence Risk Rating Outcome
Existing Controls Significant?
Risk/Hazard
Fencing and Road barrier proposed, large
All culverts and stormwater inlets with a minimum inlet dimension greater than Further assessment
pipes (DN2700), located on watercourse, Yes Good 2 3 High No
375mm, and an expected pipe-full flow travel time greater than 10 seconds. required
Limited Travel Time (<10s)
All culverts and stormwater inlets with a minimum inlet dimension greater than See Below for See Below for
Not applicable Please Select… Please Select… #N/A #N/A #N/A
375mm and a conduit containing a potential impact structure. Categories… Categories…
All culverts and stormwater inlets with a minimum inlet dimnesion greater than
See Below for See Below for
375mm that discharge to waters that are either inaccessible to a potential rescuer, Not applicable Please Select… Please Select… #N/A #N/A #N/A
Categories… Categories…
or have no suitable egress.
All culverts or stormwater inlets where the assessed safety risk is considered See Below for See Below for
Not applicable Please Select… Please Select… #N/A #N/A #N/A
unacceptable. Categories… Categories…
See Below for See Below for
Not applicable Please Select… Please Select… #N/A #N/A #N/A
Categories… Categories…
Likelihood Table Consequence Table
Level Descriptor Description Level Descriptor Description
The event will occur on
1 Almost Certain 5 Major Fatal injuries
Travel Time Calculation: an annual basis
Distance = 14.64m, pipe velocity = 1.38m/s, Travel time 10.6s. (>10s)
The event has occurred
Permanent injury or
2 Likely several times in recorded 4 Significant
psychological trauma
history
The event is likely to Broken bone or open
3 Possible 3 Moderate
occur once in 50 years flesh wound
The event has occurred
4 Unlikely 2 Minor Cuts and bruises
once before
The event has not
Wet clothes or mild
5 Rare occurred locally, but has 1 Very Minor
scare or mild trauma
occurred elsewhere
Consequence
Likelihood 1 2 3 4 5
1 Medium High High Very High Very High
2 Medium Medium High High Very High
3 Low Medium High High High
4 Low Low Medium Medium High
5 Low Low Medium Medium High