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RFI - Attachment B - Stormwater management Report · MCU20/0026
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Stormwater Management Report Proposed Residential Development 40 Park Crescent, Sunrise Beach Lot 599 on RP48112 For Sanya Holdings 11 June 2020 Ref: S20-023
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Section 2
DO C UM ENT I NFO RM AT IO N
Project Name: Stormwater Management Report for 40 Park Crescent, Sunshine Beach
Westera Partners Ref: S20-023
Westera Partners Contact:
James Crabb Phone: 3852 4333
Email: [email protected]
Jared Hill Email: [email protected]
Certified for Issue by:
Jared Hill RPEQ 19891
11 June 2020
Document Control:
Revision Author Approved for Issue Date
A J. Crabb J.Hill RPEQ 19891 11.06.2020
This report has been prepared for Sanya Holdings for the purpose of accompanying a development
application to Noosa Shire Council (NSC). This report must only be used by Sanya Holdings for this
purpose and must not be used or relied upon by any other person for any other purpose.
The assessment, conclusions or recommendations in this report are based on conditions encountered
and information received at the time of preparing the report and may not be relied upon as site
conditions or operations vary over time.
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Section 3
CO NT E NT S 1 Introduction ............................................................................................................................ 1 2 Site Description ..................................................................................................................... 1 2.1 Location and Land Use ............................................................................................................ 1 2.2 Lawful point of discharge ......................................................................................................... 2 2.3 Upstream drainage connection ................................................................................................ 2 2.4 Flooding ................................................................................................................................... 2 3 Stormwater Quantity Management ...................................................................................... 2 3.1 Catchment Summary ............................................................................................................... 2 3.1 Stormwater Detention & Infiltration .......................................................................................... 3 3.1 Hydrologic and Hydraulic Modelling ........................................................................................ 3 3.2 XP Storm Results .................................................................................................................... 5 4 Water Quality Management .................................................................................................. 7 4.1 Operational Phase ................................................................................................................... 7 4.2 Construction Phase ................................................................................................................. 8 4.2.1 Design Objectives .................................................................................................................... 8 4.2.2 Erosion and Sediment Control ............................................................................................... 10 4.2.3 Maintenance and Monitoring Requirements .......................................................................... 11 5 conclusion ............................................................................................................................ 12 6 Appendices ........................................................................................................................ A-1 Appendix A – Erosion Hazard Assessment (IECA) ............................................................................ A-1 Appendix B – Preliminary Engineering Drawings ............................................................................... B-1 Appendix C – Site Survey & Architectural Drawings .......................................................................... C-1 11 June 2020 Stormwater Management Report iii S20-023 40 Park Crescent, Sunrise Beach
Section 4
1 INT RO D UCT IO N
Westera Partners Pty Ltd was commissioned by Sanya Holdings to prepare a Stormwater Management
Report for a proposed residential development at 40 Park Crescent, Sunrise Beach.
The development involves the construction of a single dwelling and associated infrastructure.
This report documents how stormwater runoff will be managed on site in accordance with Noosa Shire
Council’s (NSC’s) requirements.
2 SIT E D ES CR I PT IO N
2. 1 Loc at i on an d L an d U se
The proposed development site is located at 40 Park Crescent, Sunrise Beach; formally known as Lot
599 on RP48112. The proposed development has an area of approximately 550m2 and is currently
occupied by an existing dwelling.
The site currently falls towards the northeast corner of the site at an average grade of approximately
24% and is bound by residential properties to the east and west, Council pathway to the north, and Park
Crescent to the south.
Refer to Figure 1 for an indicative site location and Appendix C for detailed site survey information.
Site
Figure 1 – Indicative Site Location (Nearmap, 2020)
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S20-023 40 Park Crescent, Sunrise Beach
Section 5
2. 2 Law ful poi nt of d i sch ar ge
There is existing Council stormwater drainage infrastructure traversing the site adjacent to the western
boundary, which conveys runoff from an upstream catchment and exits the site across the northern
property boundary via a 600mm dia RCP. It is assumed that minor flows from the roof of the existing
dwelling report to this existing infrastructure. Stormwater runoff from ground areas of the existing site
and major flows from the roof area appear to initially fall northeast as overland flow, prior to
concentrating and discharging to across the site boundary to the adjoining Council pathway, eventually
reporting to Sunshine Beach.
Stormwater runoff from roof areas of the proposed dwelling are proposed to be conveyed to the existing
stormwater drainage infrastructure traversing the site via the construction on new on site drainage.
Major flows from roof areas & runoff from ground areas is proposed to be directed to an underground
infiltration tank located at the rear of the site. Runoff from the tank shall discharge via infiltration or,
when at capacity, shall surcharge and discharge across the northeast property boundary per existing
conditions in a manner that results in no adverse impact to adjoining properties. Refer to Appendix B
for further information.
2. 3 Ups tr e am d ra in ag e c onne ct ion
There are no undeveloped lots upstream of the development. The provision of an upstream drainage
connection is therefore not considered to be required.
2. 4 Floo din g
According to the NSC planning scheme flood hazard overlay mapping the development site is not
subject to flooding from any sources.
3 ST O RM W AT E R Q U AN T IT Y M AN AG EM E NT
The stormwater quantity analysis of the existing and developed site conditions has been undertaken
with reference to the requirements and procedure outlined by:
Queensland Urban Drainage Manual (QUDM)
Australian Rainfall and Runoff Volumes 1 & 2 (Aust R&R)
The following section of the report discusses the proposed development’s impact on peak stormwater
runoff and total runoff volume from the site and compares the existing site condition to ensure a no
worsening effect to downstream land.
3. 1 Cat ch me nt Su mm a r y
Pre-Developed Site
The existing site consists of an existing dwelling. Stormwater runoff from roof areas of the existing
dwelling is assumed to report to the existing stormwater drainage infrastructure traversing the site, and
runoff from ground areas initially falls northeast as overland flow prior to concentrating and discharging
across the site boundary.
The existing site area is approximately 550m2 and is has approximately 44% impervious area (fi=0.44).
Post-Developed Site
The development involves the construction of a new dwelling and ground level features. Runoff from
roof areas of the development is proposed to discharge to the existing Council stormwater infrastructure
traversing the site. Major flows from roof areas and runoff from ground areas is proposed to be conveyed
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Section 6
to an infiltration tank at the rear of the site, where it shall discharge via infiltration or surcharge and fall
across the site boundary in a non-worsening manner.
The catchment area remains unchanged at approximately 550m2. The total impervious area was
calculated to be approximately 360m2 which equates to 65% fraction impervious (fi=0.65).
3. 1 Sto rmw at e r De t en t io n & I nf i ltr at ion
Stormwater runoff from ground areas of the site shall be directed to a proposed infiltration tank and
discharged from site by infiltration or by surcharging and falling across the site boundary in a manner
that results in no increase in peak flow rate and total runoff volume from pre-development levels.
The Atlantis Flo-Tank Modular tank system was adopted as part of the stormwater design. An infiltration
rate of 0.6m/d was adopted based on the subsurface profile of similar developments in the Sunshine
Beach area. Refer to Table 1 and Appendix B for further details of the proposed system.
Table 1 - Detention system details
Description Value
Tank Model 6 x Atlantis Flo-Tank - Triple
Gross Volume (m3) 2.20
Detention Capacity (m 3) 2.09
Dimensions (m) 2.06(L) x 0.97(W) x 1.31(H)
Infiltration Rate (m/d) 0.6
Catchment Area to Tank (Ha) 0.029
Catchment Area Bypassing Tank (Ha) 0.026
3. 1 H yd ro log i c and H yd r aul i c M ode ll ing
The hydraulic and hydrologic modelling software package XPSTORM was used to model the pre-
developed and post-developed flow conditions for the site. XPSTORM provides a simulation of the
natural runoff processes and the hydraulic performance of stormwater infrastructure. An integrated
1D/2D hydraulic model was developed incorporating the TUFLOW engine. The TUFLOW engine
accurately represents site specific topography, defining flow paths, discharge, storage, and variation in
flow direction in addition to modelling flood hazard.
Hydrologic Modelling
The 10% AEP event was defined as the minor storm and the 1% AEP event was defined at the major
storm for the analysis. A number of storm durations including the 10 minute, 25 minute, and 1 hour
duration were simulated for each AEP for the pre developed and post developed model.
Rainfall data for each storm duration for the 10% and 1% AEP events was obtained from the ARR 2016
data hub. The Laurenson method was utilised to calculate runoff hydrographs with the following losses:
Pervious areas – initial and continuing losses of 10mm and 3mm respectively
Impervious areas – initial and continuing losses of 2mm and 0mm respectively
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Section 7
Initially, the ensemble of storms for each duration was simulated for the pre-developed model for the
entire site, and the median storm for each duration & AEP was determined utilising the ensemble
statistics utility. The resultant storms were utilised as the design storms for the 10 minute, 25 minute,
and 1 hour duration events for each AEP.
Once the design storms were determined, the pre-developed roof catchment was simulated for the 10%
AEP and 1% AEP events. There was found to be an approximately 30% increase in runoff in the 1%
AEP simulation. Based on the results, the catchment area conveyed to the rear of the site for both the
pre-developed and post-developed model for the 1% AEP event was artificially increased by 30%
(based on modelled roof area) to account for major flows bypassing the underground stormwater
network and discharging to the rear. Further detail on catchment setup is provided below.
Hydraulic Modelling
An integrated 1D/2D model was developed to simulate the hydraulics of the stormwater drainage
network. The 1D network was limited to modelling the infiltration/detention tank in the post developed
model. Physical parameters for the storage node were calculated based on data obtained from the
manufacturer. The following parameters were utilised in developing the 2D network:
A 1m grid cell size was utilised.
The DTM was derived from LiDAR data
Manning’s roughness for of 0.06 was considered appropriate due to the land use of the site.
A 2D head boundary line with a free outfall was used to define the 2D model extent.
Model Setup
Two models were developed for the site. These are summarised as follows:
Pre-developed model
The existing site excluding the roof area was modelled as a single catchment linked to Node A.
For the 1% AEP event, the impervious catchment area was artificially increased by 30% of the
existing roof area to account for major flows bypassing the underground stormwater network.
The hydrograph of the catchment was linked to and evenly distributed across a rainfall/ flow
area grid at the rear of the site. The peak flow rate discharging across the property boundary
was measured at a flow line at the rear of the site and the total runoff volume discharging across
the property boundary was measured as the total runoff inflow at Node A.
Post-Developed Model
The developed site excluding the roof area was modelled as a single catchment linked to Node
A. Similar to the pre-developed model, the impervious catchment area was artificially increased
by 30% of the existing roof area to account for major flows bypassing the underground
stormwater network. Node A was set as a storage node to model the detention/infiltration tank.
Node A was linked to the 2D network to allow surcharging to occur. The peak flow rate
discharging across the property boundary was measured at a flow line at the rear of the site
and the total runoff volume discharging across the property boundary was measured as the
total outflow volume from Node A
The catchment data for each model is summarised in Table 2 below:
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Section 8
Table 2 - Catchment Summary
Model Event Catchment Roof Catchment Slope %
Area (Ha) Excluded (Ha) (%) Impervious
Pre-Developed 10% AEP 0.037 0.018 24 16
1% AEP 0.043 0.012 24 30
Post-Developed 10% AEP 0.028 0.027 24 34
1% AEP 0.037 0.018 24 49
3. 2 X P St or m Re su lt s
The results of the ensemble statistics utility are presented in Figure 2 & Figure 3 below.
Figure 2 - Ensemble Statistics Utility Results; 10% AEP
Figure 3 - Ensemble Statistics Utility Results; 1% AEP
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Section 9
Table 3 below compares the peak flow rates and total runoff volume for the existing and developed
model.
Table 3 - XP Storm Results
Duration Peak Flow Rate (L/s) Total Volume (m3)
AEP Median Storm
(min) Pattern Existing Developed Existing Developed
10% 10 8 21 16 (-5) 8.41 4.48 (-3.94)
25 5 16 12 (-4) 14.94 9.70 (-5.24)
60 6 13 10 (-3) 23.10 16.54 (-6.57)
1% 10 8 32 30 (-2) 15.35 11.36 (-3.99)
25 10 28 25 (-3) 27.44 21.67 (-5.77)
60 6 24 23 (-1) 43.42 35.91 (-7.51)
As shown in Table 3, the peak flow rate of stormwater runoff and the total runoff volume off site has not
increased as a result of the development. The proposed infiltration/detention tank is therefore
considered to be adequate. Results for the 10 minute duration for the 1% AEP event are outlined in
Figure 4 & 5 below.
Total runoff volume across NE
boundary (Node A inflow) = 15.35m3
Peak flow rate across
NE boundary = 32L/s
Figure 4 – XP Storm Results; Pre-Developed Model (1% AEP, 10 minute duration)
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Section 10
Total runoff volume across NE
boundary (Node A outflow) = 11.36m3
Peak flow rate across
NE boundary = 30L/s
Figure 5 – XP Storm Results; Post-Developed Model (1% AEP, 10 minute duration)
4 W AT ER Q U AL IT Y M AN AG E M ENT
4. 1 O pe r at io na l Ph a se
The proposed development is not required to meet the QLD Government’s State Planning Policy (July
2017) as the site area does not exceed 2500m2. However, stormwater quality management must still
be undertaken via the application of best management practices (BMP’s) to ensure no adverse impacts
to the downstream environment.
Pollutants typically generated during the operational phase of the development include:
Litter/gross pollutants;
Sediment;
Nutrients (N & P);
Hydrocarbons (oils and grease); and
Heavy metals.
Stormwater quality best management practices may be implemented for the development as follows:
First flush diversion system for roof water diverting the roof water for irrigation purposes
Gross pollutant filter baskets in field inlet pits collecting runoff from ground areas.
Best management practices have been deemed sufficient for the site area and land use. Refer to
Appendix B for the stormwater management drawing.
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Section 11
4. 2 Con st ruc t io n Ph a se
Management of stormwater runoff during construction and the implementation of an erosion & sediment
control program is necessary to avoid impacts to receiving waters from pollutants typically generated
during the construction phase. Typical pollutants are described in Table 6 below:
Table 4 – Pollutants Typically Generated During the Construction Phase
Pollutant Sources
Litter (Gross Pollutants) Paper, construction packaging, food packaging, cement bags.
Sediment Unprotected exposed soils and stockpiles during earthworks and building.
Hydrocarbons Fuel and oil spills, leaks from construction equipment.
Toxic materials Cement slurry, asphalt prime, solvents, cleaning agents, wash waters.
pH altering substances Acid sulphate soils, cement slurry and wash waters.
In addition to the degradation of receiving waters, impacts of inadequate erosion and sediment control
downstream from the site include:
traffic safety problems;
blocked drains;
local flooding problems;
aesthetic pollution of drainage paths; and
damage to local ecosystems.
4.2.1 De si gn O bj e ct iv es
Management of stormwater runoff during construction should be undertaken in accordance with
Appendix 2 of the SPP (July 2017). The SPP outlines the design objectives for construction phase
stormwater management. These are presented in Table 5, Table 6 and Table 7.
Table 5 – SPP Appendix 2: Part 1 Construction Phase – Stormwater Management Design Objectives
Issue Desired Outcomes
Drainage Control 1. Manage stormwater flows around or through areas of exposed soil to
avoid contamination.
2. Manage sheet flows in order to avoid or minimise the generation of rill or
gully erosion.
3. Provide stable concentrated flow paths to achieve the construction
phase stormwater management design objectives for temporary
drainage works (part 2).
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Section 12
Issue Desired Outcomes
4. Provide emergency spillways for sediment basins to achieve the
construction phase stormwater management design objectives for
emergency spillways on temporary sediment basins (part 3).
Erosion Control 1. Stage clearing and construction works to minimise the area of exposed
soil at any one time.
2. Effectively cover or stabilise exposed soils prior to predicted rainfall.
3. Prior to completion of works for the development, and prior to removal
of sediment controls, all site surfaces must be effectively stabilised
using methods which will achieve effective short-term stabilisation.
Sediment Control 1. Direct runoff from exposed site soils to sediment controls that are
appropriate to the extent of disturbance and level of erosion risk.
2. All exposed areas greater than 2500 metres must be provided with
sediment controls which are designed, implemented and maintained
to a standard which would achieve at least 80% of the average annual
runoff volume of the contributing catchment treated (i.e. 80%
hydrological effectiveness) to 50mg/L Total Suspended Solids (TSS) or
less, and pH in the range (6.5–8.5).
Litter, Hydrocarbons and 1. Remove gross pollutants and litter.
other contaminants
2. Avoid the release of oil or visible sheen to released waters.
3. Dispose of waste containing contaminants at authorised facilities.
Waterway Stability and 1. Where measures are required to meet post-construction waterway
flood flow management stability objectives, these are either installed prior to land disturbance
and are integrated with erosion and sediment controls, or equivalent
alternative measures are implemented during construction.
2. Earthworks and the implementation of erosion and sediment controls
are undertaken in ways which ensure flooding characteristics
(including stormwater quantity characteristics) external to the
development site are not worsened during construction for all events up
to and including the 1 in 100 year ARI (1% AEP).
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Section 13
Table 6 – SPP Appendix 2: Part 2 Construction Phase – Stormwater Management Design Objectives
for Temporary Drainage Works
Temporary Drainage Works Anticipated Operation Design Life and Minimum
Design Storm Event
<12 Months 12-24 Months >24 Months
Drainage Structure 1 in 2 year 1 in 5 year 1 in 10 year
ARI/39% AEP ARI/18% AEP ARI/10% AEP
Where located immediately up-slope of an 1 in 10 year ARI/10% AEP
occupied property that would be adversely
affected by the failure or overtopping of the
structure
Culvert Crossing 1 in 1 year ARI/63% AEP
Table 7 – SPP Appendix 2: Part 3 Construction Phase – Stormwater Management Design Objectives
for Emergency Spillways on Temporary Sediment Basins
Drainage Structure Anticipated Operation Design Life and Minimum
Design Storm Event
<3 Months 3-12 Months >12 Months
Emergency spillways on temporary 1 in 10 year 1 in 20 year 1 in 50 year
sediment basins ARI/10% AEP ARI/5% AEP ARI/2% AEP
Best practice erosion and sediment controls must be installed to minimise the discharge of sediment
laden runoff during construction and to achieve the objectives outlined in Tables 7-9. This is discussed
in the following section.
4.2.2 E ro sio n and Se di men t Co n tr ol
The proposed development received an erosion hazard score of 19. Refer to Appendix A for details.
Erosion and sediment control plans shall be developed during the detailed design phase in accordance
with the requirements outlined in the International Erosion Control Association (IECA) 2008 best
practice documentation. Erosion and sediment control plans are based on three sets of control
measures:
drainage control;
erosion control; and
Sediment control.
These control measures must be continually maintained in an effective operational condition and
amended as required to minimise environmental harm. Sediment disposal from site is to occur to the
satisfaction of NSC and the following release limits of stormwater captured in a sediment basin shall be
adhered to:
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Section 14
50mg/L of total suspended solids (TSS) as a maximum concentration;
Turbidity (NTU) value less than 10% above background;
pH value must be in a range 6.5-8.5 except where, and to the extent that, the natural receiving
waters lie outside this range.
Defects in erosion and sediment control devices, such as sediment fences, are to be inspected and
documented. Upon Inspection, the contractor is to determine whether the device should be replaced or
repaired. Documentation is to include how the damage was caused and what measures can be
implemented to reduce the possibility of repeat occurrences. Any damage to either permanent or
temporary water quality control structures or devices is to be immediately rectified at the contractor’s
expense.
The effectiveness of the erosion and sediment control devices can be monitored by visual audits. All
ESC measures are to be inspected:
at least daily (when work is occurring on site) or weekly (when work is not occurring on site);
within 24 hours of expected rain; and
within 18 hours of a rainfall event (i.e. an event of sufficient intensity and duration to mobilise
sediment on site).
Drainage paths are to be inspected to ensure the sediment fences are not being bypassed as a result
of soil erosion.
Sediment laden runoff shall be prevented from entering neighbouring properties. This shall be achieved
by landscaping disturbed areas immediately and prior to a rainfall event.
4.2.3 M aint en an ce and M onit o ri ng R equ ir em ent s
Periodic maintenance and monitoring of stormwater devices proposed in this report is crucial to ensure
effective operation and design life.
Inspect field inlet grates, pits and underground pipes for blockage or damage at least 6 monthly or after
significant rainfall event. The filter baskets shall be inspected and maintained preferably by the
manufacturer to avoid damage to units and to ensure adequate cleaning and record keeping. For the
first 12 months routine inspections of filter baskets shall be carried out monthly with routine clean out
at alternate months. Results of the initial 12 months maintenance program shall be used to determine
future maintenance intervals. Refer manufactures maintenance and monitoring methodology for
specific details. Maintenance of ESC measures must occur in accordance with Table 10.
Table 8 - ESC maintenance requirements.
ESC Measure Maintenance Trigger Timeframe for Completion
of Maintenance
Sediment basins When settled sediment exceeds Within 7 days of the
the volume of the sediment inspection.
storage zone
Other ESC measures The capacity of ESC measures By the end of the day.
falls below 75%.
Sediment accumulation on ESC devices is to be removed and disposed of to the satisfaction of NSC.
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Section 15
5 CO N CLU S IO N This SWMP outlines how stormwater runoff from the site will be managed in order to not adversely impact the receiving environment. Minor flows from the roof of the proposed dwelling shall be directed to existing Council stormwater infrastructure traversing the site via the construction of new on site drainage. Major flows from the roof of the proposed dwelling and runoff from ground level areas shall be conveyed to an underground detention and infiltration tank with approximately 2.1m3 detention capacity at the rear of the site. Runoff from the tank shall discharge from the site either by infiltration or shall surcharge and fall across the north eastern property boundary in a non-worsening manner per existing conditions, eventually reporting to Sunshine Beach. The final layout & configuration of the tank shall be confirmed at the detailed design phase. Stormwater quality treatment shall be provided via best management practices. This could be achieved by first flush diverters directing runoff for irrigation of landscaped areas and/or the installation of filter baskets in field inlet pits. Based on the scale of the proposed development, and typical pollutants produced, these measures are considered adequate. By implementing the proposed stormwater management system, and providing adequate maintenance, the downstream environment and neighbouring properties will not experience any adverse deterioration of water quality as a result of the proposed development. 11 June 2020 Stormwater Management Report 12 S20-023 40 Park Crescent, Sunrise Beach
Section 16
6 AP P E N D IC E S Ap p end ix A – E ro sio n H az ar d As s e s sm en t (I E C A ) 11 June 2020 Stormwater Management Report A-1 S20-023 40 Park Crescent, Sunrise Beach
Section 17
Best Practice Erosion And Sediment Control Erosion Hazard Assessment Form
Erosion Hazard Assessment Form
Condition Points Score Trigger
value
AVERAGE SLOPE OF DISTURBANCE AREA [1]
not more than 3% [3% 33H:1V] 0
more than 3% but not more than 5% [5% = 20H:1V] 1
6 4
more than 5% but not more than 10% [10% = 10H:1V] 2
more than 10% but not more than 15% [15% 6.7H:1V] 4
more than 15% 6
SOIL CLASSIFICATION GROUP (AS1726) [2]
GW, GP, GM, GC 0
SW, SP, OL, OH 1 3
SM, SC, MH, CH 2
ML, CL, or if imported fill is used, or if soils are untested 3
EMERSON (DISPERSION) CLASS NUMBER [3]
Class 4, 6, 7, or 8 0
Class 5 2 4 6
Class 3, (default value if soils are untested) 4
Class 1 or 2 6
DURATION OF SOIL DISTURBANCE [4]
not more than 1 month 0
more than 1 month but not more than 4 months 2 2 6
more than 4 months but not more than 6 months 4
more than 6 months 6
AREA OF DISTURBANCE [5]
not more than 1000 m2 0
more than 1000 m2 but not more than 5000 m2 1 0 4
more than 5000 m2 but not more than 1 ha 2
more than 1 ha but not more than 4 ha 4
more than 4 ha 6
WATERWAY DISTURBANCE [6]
No disturbance to a watercourse, open drain or channel 0
0 2
Involves disturbance to a constructed open drain or channel 1
Involves disturbance to a natural watercourse 2
REHABILITATION METHOD [7]
Percentage of area (relative to total disturbance) revegetated by seeding
without light mulching (i.e. worst-case revegetation method).
not more than 1% 0 0
more than 1% but not more than 5% 1
more than 5% but not more than 10% 2
more than 10% 4
RECEIVING WATERS [8]
Saline waters only 0 0
Freshwater body (e.g. creek or freshwater lake or river) 2
SUBSOIL EXPOSURE [9]
No subsoil exposure except of service trenches 0 2
Subsoils are likely to be exposed 2
EXTERNAL CATCHMENTS [10]
No external catchment 0
1
External catchment diverted around the soil disturbance 1
External catchment not diverted around the soil disturbance 2
ROAD CONSTRUCTION [11]
No road construction 0 0
Involves road construction works 2
pH OF SOILS TO BE REVEGETATED [12]
more than pH 5.5 but less than pH 8 0 1
other pH values, or if soils are untested 1
Total Score [13] 19 16
IECA (Australasia) November 2008 Page 1
Section 18
Best Practice Erosion And Sediment Control Erosion Hazard Assessment Form
Explanatory notes
Requirements: Specific issues or actions required by the proponent.
Warnings: Issues that should be considered by the proponent.
Comments: General information relating to the topic.
[1] REQUIREMENTS:
For sites with an average slope of proposed land disturbance greater than 10%, a
preliminary ESCP must be submitted to the regulatory authority for approval
during planning negotiations.
Proponents must demonstrate that adequate erosion and sediment control
measures can be implemented on-site to effectively protect downstream
environmental values.
If site or financial constraints suggest that it is not reasonable or practicable for
the prescribed water quality objectives to be achieved for the proposal, then the
proponent must demonstrate that alternative designs or construction techniques
(e.g. pole homes, suspended slab) cannot reasonably be implemented on the
site.
WARNINGS:
Steep sites usually require more stringent drainage and erosion controls than
flatter grade sites.
COMMENTS:
The steeper the land, the greater the need for adequate drainage controls to
prevent soil and mulch from being washed from the site.
[2] REQUIREMENTS:
If the actual soil K-factor is known from soil testing, then the Score shall be
determined from Table 1.
If a preliminary ESCP is required during planning negotiations, then it must be
demonstrated that adequate space is available for the construction and operation
of any major sediment traps, including the provision for any sediment basins and
their associated embankments and spillways. It must also be demonstrated that
all reasonable and practicable measures can be taken to divert the maximum
quantity of sediment-laden runoff (up to the specified design storm) to these
sediment traps throughout the construction phase and until the contributing
catchment is adequately stabilised against erosion.
WARNINGS:
The higher the point score, the greater the need to protect the soil from raindrop
impact and thus the greater the need for effective erosion control measures. A
point score of 2 or greater will require a greater emphasis to be placed on
revegetation techniques that do not expose the soil to direct rainfall contact
during vegetation establishment, e.g. turfing and Hydromulching.
COMMENTS:
Table 2 provides an indication of soil conditions likely to be associated with a
particular Soil group based on a statistical analysis of soil testing across NSW.
This table provides only an initial estimate of the likely soil conditions.
IECA (Australasia) November 2008 Page 2
Section 19
Best Practice Erosion And Sediment Control Erosion Hazard Assessment Form
The left-hand-side of the table provides an indication of the type of sediment
basin that will be required (Type C, F or D). The right-hand-side of the table
provides an indication of the likely erodibility of the soil based on the Revised
Universal Soil Loss Equation (RUSLE) K-factor.
Table 3 provides some general comments on the erosion potential of the various
soil groups.
Table 1 – Score if soil K-factor is known
RUSLE soil erodibility K-factor
K < 0.02 0.02<K<0.04 0.04<K<0.06 K > 0.06
Score 0 1 2 3
Table 2 – Statistical analysis of NSW soil data [1]
Unified Likely sediment basin Probable soil erodibility K-factor (%) [2]
Soil classification (%)
Class Dry Wet Low Moderate High Very High
System
Type C Type F Type D K < 0.02 0.02<K<0.04 0.04<K<0.06 K > 0.06
GM 30 58 12 12 51 26 12
GC 42 33 25 13 71 17 0
SW 40 48 12 49 39 12 0
SP 53 32 15 76 18 5 1
SM 21 67 12 26 48 25 1
SC 26 50 24 16 64 18 2
ML 5 63 32 4 35 45 16
CL 9 51 39 12 56 19 13
OL 2 80 18 34 61 5 1
MH 12 41 48 15 19 41 25
CH 5 44 51 39 43 11 7
Notes: [1] Analysis of soil data presented in Landcom (2004).
[2] Soil erodibility based on Revised Universal Soil Loss Equation (RUSLE) K-factor.
Unified Soil Classification System (USCS)
GW Well graded gravels, gravel-sand mixtures, little or no fines
GP Poorly graded gravels, gravel-sand mixture, little or no fines
GM Silty gravels, poorly graded gravel-sand-silt mixtures
GC Clayey gravels, poorly graded gravel-sand-clay mixtures
SW Well graded sands, gravelly sands, little or no fines
SP Poorly graded sands, gravelly sands, little or no fines
SM Silty sands, poorly graded sand-silt mixtures
SC Clayey sands, poorly graded sand-clay mixtures
ML Inorganic silts & very fine sands, rock flour, silty or clayey fine sands with slight plasticity
CL Inorganic clays, low–medium plasticity, gravelly clays, sandy clays, silty clays, lean clays
OL Organic silts and organic silt-clays of low plasticity
MH Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic silts
CH Inorganic clays of high plasticity, fat clays
OH Organic clays of medium to high plasticity
IECA (Australasia) November 2008 Page 3
Section 20
Best Practice Erosion And Sediment Control Erosion Hazard Assessment Form
Table 3 – Typical properties of various soil groups [1]
Soil Groups Typical properties [2]
GW, GP Low erodibility potential.
GM, GC Low to medium erodibility potential.
May create turbid runoff if disturbed as a result of the release of silt
and clay particles.
SW, SP Low to medium erodibility potential.
SM, SC Medium erodibility potential.
May create turbid runoff if disturbed as a result of the release of silt
and clay particles.
MH, CH Highly variable (low to high) erodibility potential.
Will generally create turbid runoff if disturbed.
ML, CL High erodibility potential.
Tendency to be dispersive.
May create some turbidity in runoff if disturbed.
Note: [1] After Soil Services & NSW DLWC (1998).
[2] Any soil can represent a high erosion risk if the binding clays or silts are unstable.
Table 4 provides general guidelines on the suitability of various soil groups to various
engineering applications.
Table 4 – Engineering suitability based on Unified Soil Classification [1]
Embankments
USC Fill Slope Untreated
Unified Soil Class Water Non
Group stability roads
retaining water
retaining
Well graded gravels GW Unsuitable Excellent Excellent Excellent Average
Poorly graded gravel GP Unsuitable Average Excellent Average Unsuitable
Silty gravels GM Unsuitable Average Good Average Average
Clayey gravels GC Suitable Average Good Average Excellent
Well graded sands SW Unsuitable Excellent Excellent Excellent Average
Poorly graded sands SP Unsuitable Average Good Average Unsuitable
Silty sands SM Suitable [2] Average Average Average Poor
Clayey sands SC Suitable Average Average Average Good
Inorganic silts ML Unsuitable Poor Average Poor Unsuitable
Inorganic clays CL Suitable [2] Good Average Good Poor
Organic silts OL Unsuitable Unsuitable Poor Unsuitable Unsuitable
Inorganic silts MH Unsuitable Poor Poor Poor Unsuitable
Inorganic clays CH Suitable [2] Average Unsuitable Average Unsuitable
Organic clays OH Unsuitable Unsuitable Unsuitable Unsuitable Unsuitable
Highly organic soils Pt Unsuitable Unsuitable Unsuitable Unsuitable Unsuitable
Notes: [1] Modified from Hazelton & Murphy (1992)
[2] Suitable only after modifications to soil such as compaction and/or erosion protection
IECA (Australasia) November 2008 Page 4
Section 21
Best Practice Erosion And Sediment Control Erosion Hazard Assessment Form
[3] If the soils have not been tested for Emerson Class, then adopt a score of 4.
REQUIREMENTS:
Works proposed on sites containing Emerson Class 1 or 2 soils have a very high
pollution potential and must submit a conceptual ESCP to the regulatory authority
for review and/or approval (as required by the authority) during planning
negotiations.
WARNINGS:
Class 3 and 5 soils disturbed by cut and fill operations or construction traffic are
highly likely to discolour stormwater (i.e. cause turbid runoff). Chemical
stabilisation will likely be required if these soils are placed immediately adjacent
to a retaining wall. Any disturbed Class 1, 2, 3 and 5 soils that are to be
revegetated must be covered with a non-dispersive topsoil as soon as possible
(unless otherwise agreed by the regulatory authority).
Class 1 and 2 soils are highly likely to discolour (pollute) stormwater if exposed to
rainfall or flowing water. Treatment of these soils with gypsum (or other suitable
substance) will most likely be required. These soils should not be placed directly
behind a retaining wall unless it has been adequately treated (stabilised) or
covered with a non-dispersible soil.
[4] The duration of disturbance refers to the total duration of soil exposure to rainfall
up until a time when there is at least 70% coverage of all areas of soil.
REQUIREMENTS:
All land developments with an expected soil disturbance period greater than 6
months must submit a conceptual ESCP to the regulatory authority for review
and/or approval (as required by the authority) during planning negotiations.
COMMENTS:
Construction periods greater than 3 months will generally experience at least
some significant storm events, independent of the time of year that the
construction (soil disturbance) occurs.
[5] REQUIREMENTS:
Development proposals with an expected soil disturbance in excess of 1ha must
submit a conceptual ESCP to the regulatory authority for review and/or approval
(as required by the regulatory authority) during planning negotiations.
The area of disturbance refers to the total area of soil exposed to rainfall or dust-
producing winds either as a result of:
(a) the removal of ground cover vegetation, mulch or sealed surfaces;
(b) past land management practices;
(c) natural conditions.
WARNINGS:
A Sediment Basin will usually be required if the disturbed area exceeds 0.25ha
(2500m2) within any sub-catchment (i.e. land flowing to one outlet point).
COMMENTS:
For soil disturbances greater than 0.25ha, the revegetation phase should be
staged to minimise the duration for which soils are exposed to wind, rain and
concentrated runoff.
IECA (Australasia) November 2008 Page 5
Section 22
Best Practice Erosion And Sediment Control Erosion Hazard Assessment Form
[6] REQUIREMENTS:
All developments that involve earthworks or construction within a natural
watercourse (whether that watercourse is in a natural or modified condition) must
submit a conceptual ESCP to the regulatory authority for review and/or approval
(as required by the regulatory authority) during planning negotiations.
Permits and/or licences may be required from the State Government, including
possible submission of the ESCP to the relevant Government department.
[7] REQUIREMENTS:
No areas of soil disturbance shall be left exposed to rainfall or dust-producing
winds at the end of a development without an adequate degree of protection
and/or an appropriate action plan for the establishment of at least 70% cover.
COMMENTS:
Grass seeding without the application of a light mulch cover is considered the
least favourable revegetation technique. A light mulch cover is required to
protect the soil from raindrop impact, excessive temperature fluctuations, and the
loss of essential soil moisture.
[8] COMMENTS:
All receiving waters can be adversely affected by unnatural quantities of
sediment-laden runoff. Freshwater ecosystems are generally more susceptible to
ecological harm resulting from the inflow of fine or dispersible clays than saline
water bodies. The further inland a land disturbance is, the greater the potential
for the released sediment to cause environmental harm as this sediment travels
towards the coast.
For the purpose of this clause it is assumed that all sediment-laden runoff will
eventually flow into saline waters. Thus, sediment-laden discharges that flow first
into freshwater are likely to adversely affect both fresh and saline water bodies
and are therefore considered potentially more damaging to the environment.
This clause does not imply that sediment-laden runoff will not cause harm to
saline waters.
[9] COMMENTS:
This clause refers to subsoils exposed during the construction phase either as a
result of past land practices or proposed construction activities. The exposure of
subsoils resulting from the excavation of minor service trenches should not be
considered.
[10] WARNINGS:
The greater the extent of external catchment, the greater the need to divert up-
slope stormwater runoff around any soil disturbance.
COMMENTS:
The ability to separate “clean” (i.e. external catchment) stormwater runoff from
“dirty” site runoff can have a significant effect on the size, efficiency and cost of
the temporary drainage, erosion, and sediment control measures.
IECA (Australasia) November 2008 Page 6
Section 23
Best Practice Erosion And Sediment Control Erosion Hazard Assessment Form
[11] REQUIREMENTS:
Permission must be obtained from the owner of a road reserve before placing
any erosion and sediment control measures within the road reserve.
WARNINGS:
Few sediment control techniques work efficiently when placed on a road and/or
around roadside stormwater inlets. Great care must be taken if sediment control
measures are located on a public roadway, specifically:
safety issues relating to road users;
the risk of causing flooding on the road or within private property.
The construction of roads (whether temporary or permanent) will usually modify
the flow path of stormwater runoff. This can affect how “dirty” site runoff is
directed to the sediment control measures.
COMMENTS:
“On-road” sediment control devices are at best viewed as secondary or
supplementary sediment control measures. Only in special cases and/or on very
small projects (e.g. kerb and channel replacement) might these controls be
considered as the “primary” sediment control measure.
[12] WARNINGS:
Soils with a pH less than 5.5 or greater than 8 will usually require treatment in
order to achieve satisfactory revegetation. Soils with a pH of less than 5
(whether naturally acidic or in acid sulfate soil areas) may also limit the choice of
chemical flocculants (e.g. Alum) for use in the flocculation of Sediment Basins.
[13] REQUIREMENTS:
A preliminary ESCP must be submitted to the local government for approval
during the planning phase for any development that obtains a total point score of
17 or greater or when any trigger value is scored or exceeded.
IECA (Australasia) November 2008 Page 7
Section 24
Ap p end ix B – P re li mi na r y Eng in ee r ing D r a w ings 11 June 2020 Stormwater Management Report B-1 S20-023 40 Park Crescent, Sunrise Beach
Section 25
LEGEND
PRELIMINARY SERVICES PLAN
CATCHMENT SUMMARY
SECTION SECTION
PRELIMINARY
SUNSHINE COAST GOLD COAST SURVEYOR No. DATE REVISIONS
SHEET APPROVED DESIGNED
SHEET NUMBER
Suite 2, Norval Corporate Centre, Level 3
13 Norval Ct, Maroochydore 17 Welch St, Southport
T 0431 803 337
E [email protected]
T 07 5571 1599 F 07 5571 1330
E [email protected] PROJECT DRAWN
PARTNERS BRISBANE NORTHERN NSW USE FIGURED DIMENSIONS ONLY. DO NOT SCALE, IF A DISCREPANCY ARISES CHECK WITH THE
PROJECT ENGINEER AND/OR SUPERVISING AUTHORITY. DO NOT WORK FROM REDUCED SCALE LOCATION DATE DRAWN
REVISION
Level 2 Limestore, 11 Sailfish Way, Kingscliff
33 Longland St, Newstead T 02 6674 8047 F 02 6674 8049
DRAWINGS (A1-A3 SIZE PAPER). COPYRIGHT OF ALL DRAWINGS & WORKS EXECUTED FROM PROJECT NUMBER
THEM IS VESTED IN WESTERA PARTNERS AND USE OF THERE FORE WITHOUT PERMISSION IS
T 07 3852 4333 F 07 3852 4777 E [email protected] STRICTLY PROHIBITED! IT IS THE BUILDERS RESPONSIBILITY TO ENSURE ALL WORKS ARE
www.westerapartners.com.au ABN 52 097 417 975 E [email protected] CARRIED OUT WITH DUE CARE AND DILIGENCE TO COMPLY WITH THE CONTRACT DOCUMENTS. CLIENT For and on behalf of
WESTERA PARTNERS PTY. LTD.
FILE NAME
Section 26
Ap p end ix C – Si t e Su rv e y & Ar ch it ect ur a l Dr aw ing s 11 June 2020 Stormwater Management Report C-1 S20-023 40 Park Crescent, Sunrise Beach
Section 27
SURVEYING
AJS SURVEYS
. PLANNING . DEVELOPMENT
Sewer Line
Approximate only
Plotted from
Council Records
7
.5
18
P
Stormwater Line
Approximate only
Plotted from
Ti
m
Council Records
be
r
Fe
nc
P: 07 3823 2144 E: [email protected]
e
A
Incorporating LJ Hewitt & Co
5
.1
W:www.ajssurveys.com.au
18
5
.8
Gutter
4
17
.0
18
Level
T
6
25.52
.9
17
DECK
. 00
1 80 0
2
.5
T*S1/100
17
.
18
6
.7
17
4
TWO STOREY
.6
Septic
17
Roof
1
.1
18
Level Tank
ce 0
0
.5 5
17 . 5
H
.8
RENDERED en
17
5
8
3
26.22
.0
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.2
F
18
17
17
7
.8
er
3
17
17
.6
b
Tap
19
BUILDING Ti
m T*S2/200
1
.3
17
0
.4
17
Garden
8
0
.9
16
.5
1850
Ridge
6
.6
0 T*S2/150
3
17
.6
Level .5
18
18 .
0
8
27.13 Timber
1 17.4
7
W
.0
Section 28
3
.1
7
Retaining
.6
20
18
5
4
.9
.1
17
Wall
16
17
00
1
.7
4
17 .
Gutter
.5
16
17
8
Level
.0
T*S1/100 T*S12/650
17
19 . 00
25.32
7
.1
18
Deck
5
.3
16
Ti
Level
0
1
0
.1
.3
T*S1/100
17 0
1
m
6
.6
.5
17
19
4
.7
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17
16
.8
be
599
22.93
16
0
r
.5
16
Fe
19 . 50
16
nc
DECK
T*S1/150
7
.5
e
19
Gutter
6
Garden
.9
A
15
Level
RP 48112 Grass
1
2
.9
2
.0
25.82
0
.8
00 19
.6
17
3
17 .56
16
.4
18
T*S4/300
1
16
6
17
.2
DECK
.7
16
8
0
.0
0
19
.0
20 .
Gutter
0
e
nc
3
Gutter
6.
.6
Fe Level
The text continues on section 29.
Used in these records
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