Stormwater Quality and Flow
Management Guidelines
July 2013
Stormwater Quality and Flow Management Guidelines
July 2013
1. Introduction
The Stormwater Quality and Flow Management Guidelines provide a framework to ensure development for urban
purposes within Logan City helps to achieve the outcomes of the State Planning Policy 4/10 Healthy Waters (SPP 4/10)
and the South East Queensland Regional Plan 2009-2031 (SEQ Regional Plan).
This guideline applies to all assessable development within Logan City. This guideline is intended to provide guidance on
Logan City’s stormwater quality and flow management requirements consistent with the SPP 4/10 and the SEQ Regional
Plan.
These guidelines:
• identify development that must achieve the stormwater management design objectives;
• set design objectives that all applicable development must achieve;
• outline information required to be submitted to demonstrate compliance with the design objectives; and
• outline Council’s design standards and specifications
2. Stormwater management design objectives
The stormwater management design objectives and their associated aims are:
• Stormwater Quality Management Design Objective which aims to protect receiving water quality by limiting the
quantity of key pollutants discharged in stormwater from urban development.
•
Waterway Stability Management Design Objective which aims to prevent exacerbated in-stream erosion
downstream of urban areas by controlling the magnitude and duration of sediment-transporting flows.
•
Frequent Flow Management Design Objective which aims to protect in-stream ecosystems from the significant
effects of increased runoff frequency by capturing the initial portion of runoff from impervious areas. This approach
ensures that the frequency of hydraulic disturbance to in-stream ecosystems in developed catchments is similar to
pre-development conditions.
3. Applicable development
The stormwater management design objectives apply to applicable new development in accordance with Section 2.7 of
SPP 4/10.
4. Stormwater quality management design objective
4.1 Objective
The intent of the stormwater quality design objective is to reduce the impacts of urban development on pollutant
loads discharged to receiving waters in the operational phase. The stormwater quality design objective is to achieve
the following minimum reductions in total pollutant load, compared with that in untreated stormwater runoff, from the
developed part of the site:
•
•
•
•
80% reduction in total suspended solids;
60% reduction in total phosphorus;
45% reduction in total nitrogen; and
90% reduction in gross pollutants.
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July 2013
4.2 Alternative Acceptable Compliance
Development specified in Section 3 of this guideline is considered to have complied with the stormwater quality design
objective where the development outcome achieves site coverage with less than 25% impervious area and the capture
and management of the first 10mm of stormwater runoff per day from all impervious areas. Management of the captured
runoff should include one or more of the following:
•
•
•
evaporation of stormwater;
reuse of stormwater (including collection and use of roof water); and
infiltration to native soils or filtration through an appropriately designed soil and plant stormwater treatment system
(e.g. bio-retention).
4.3 Demonstrating Compliance
This section outlines Council’s information requirements with respect to stormwater quality at each stage of the
development approval process. A ‘Deemed to Comply Solution’ or a Conceptual Stormwater Quality Management
Plan (CSQMP) must be submitted with the initial development application (i.e. Material Change of Use (MCU) or
Reconfiguration of Lot (RoL) application). Following MCU or RoL approval, a Detailed Stormwater Quality Management
Plan (DSQMP) must be submitted with an operational works application.
Alternatively, for applicable development, a stormwater offset may be accepted in accordance with the SPP 4/10 (refer to
Section 4.3.2).
4.3.1 Preparation of a ‘Deemed to Comply Solution’
The purpose of the solutions is to streamline the development approval process, while still demonstrating compliance with
the stormwater quality design objectives. The option of submitting a ‘Deemed to Comply Solution’ as an alternative to a
CSQMP is available to all types and scales of development provided all documentation and requirements of the Water
Sensitive Urban Design (WSUD) Deemed to Comply Solutions are met. Refer to the WSUD Deemed to Comply Solutions
for South East Queensland (2009) for reporting and other requirements of a ‘Deemed to Comply’ solution.
4.3.2 Stormwater Quality Offset
4.3.2.1 Applicability
Under the SPP 4/10, stormwater quality offsets may be utilised where the provision of on-site treatment is determined
to be ‘unfeasible’. Offsets are to deliver an alternative stormwater quality improvement project that achieves a similar
or better water quality outcome as that required by the proposed development. Council will consider acceptance of a
stormwater quality offset in the form of a financial contribution in lieu of on-site treatment for proposed developments
where:
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•
•
the waterway stability design objective and frequent flow management design objective are not applicable (refer to
Sections 5 and 6 of this guideline); and
Council has appropriate stormwater quality offset delivery projects designed and costed that will achieve a similar or
better water quality outcome as that required by the proposed development at the time the development application
is made; and
on-site treatment is determined to be unfeasible.
Advice Note: Where the waterway stability design objective and frequent flow design objective are not applicable, the proposed development would
typically be a smaller scale infill type development in a predominantly urbanised catchment and it is likely on-site treatment would be considered
unfeasible. Conversely, for proposed developments where the waterway stability design objective and frequent flow design objective are applicable, the
development would typically be a larger scale and/or ‘greenfield’ type development and on-site treatment would likely be considered to be feasible.
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The following factors may be considered to determine when on-site treatment is ‘unfeasible’:
•
•
•
infill development where the site is constrained by size, topography, gradients etc to the extent that it is unfeasible to
integrate WSUD devices without detracting from the amenity and aesthetic values of the development; or
the size of development area means land required for treatment system(s) would have significant impact on
development viability; or
costs of installation and maintenance of the treatment system(s) would make the development economically
unfeasible.
4.3.2.2 Calculation of Offsets
Under SPP 4/10, offsets are to deliver an alternative stormwater quality improvement project that achieves a similar or
better water quality outcome. The amount of offset charged for a particular development will be determined by the cost
to Council of designing, constructing and establishing stormwater quality projects to achieve this outcome. The actual
charge for a particular development will be determined by the weighted average cost of applicable Council stormwater
quality projects at the time the application is assessed, and the area and type of development proposed.
Applicants wishing to pay an offset in lieu of implementing on-site treatment are advised to contact Council’s Environment
and Sustainability Branch on 3412 4620 or via email eap@logan.qld.gov.au to determine the eligibility and amount of
payment required for their development.
4.3.3 Preparation of a Conceptual Stormwater Quality Management Plan
A CSQMP may be submitted for applicable development as an alternative to a ‘Deemed to Comply Solution’ to
demonstrate compliance with the stormwater quality design objectives. The CSQMP should be concise and include
only relevant information to the proposed development. Information to be included in the CSQMP will depend on the
development type and proposed treatment measures but at a minimum will include the following.
4.3.3.1 Site Assessment
Existing topography and drainage
Describe the existing topography and the existing drainage within, upstream and downstream of the development site.
Details should include the size, location and levels of any existing drainage measures.
Soils
Describe the site’s soils. The level of investigation will depend on the proposed design of the stormwater treatment. For
example, a detailed soil evaluation in accordance with AS/NZS 1547:2000 Clause 4.1.3 would be required to support
any bio-retention system or constructed wetland designed without an impermeable liner or if stormwater infiltration is
proposed. The location of any acid sulfate soils must also be identified.
Existing site plan
Provide an existing site plan showing contours, flow pathways, development boundaries, waterway and drainage invert
levels, soil types, existing vegetation and any vegetation to be retained must also be provided.
4.3.3.2 Development Details
Site configuration
Tabulate the total area for each land use type such as road surfaces, driveways, roof surfaces, landscape areas,
pavement areas, stormwater treatment areas and any other categories specific to the site.
Earthworks and catchment details
Provide details of the conceptual earthworks and catchments and sub-catchments. Include details of the proposed
drainage network including conceptual levels to demonstrate that stormwater can enter and drain freely from stormwater
treatment measures.
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Proposed development scale plan layout
Catchment details, the conceptual drainage network with invert levels, the location of all stormwater treatment measures
and the location of existing and proposed infrastructure such as sewer and water must be shown on a scale plan layout.
4.3.3.3 Treatment Train
Describe each treatment train for each sub-catchment including how each type of pollutant (primary, secondary and
tertiary) will be treated. Ensure that primary pollutant treatment measures are located at the beginning of the treatment
train and tertiary treatment measures are positioned at the end. Provide details of each individual treatment device
including total footprint, treatment area, invert levels, coarse sediment management, maintenance access and design
flows. Specify whether the stormwater treatment system will be privately maintained or handed over to Council to
manage.
The above information should be displayed on scale plan and section drawings. The scale plan drawing must show:
• how stormwater is conveyed to the stormwater treatment devices;
• the location of all stormwater treatment devices including filter areas and batters with respect to the development
layout;
• surrounding ground levels;
• conceptual design levels for each treatment device and receiving drainage invert levels;
• scour protection and coarse sediment management devices; and
• maintenance access.
Section drawings must show:
• conceptual design levels for each treatment device and receiving drainage invert levels;
• scour protection and coarse sediment management devices; and
• any batters, embankments or retaining walls.
4.3.3.4 Model Pollutant Load Reduction
Use the Model for Urban Stormwater Improvement Conceptualisation (MUSIC) to model pollutant removal.
To demonstrate that MUSIC has been utilised correctly, all modelling and reporting is to be carried out in accordance with
the most current version of the Water by Design MUSIC Modelling Guidelines. A copy of the MUSIC modelling on CD
(saved as a .sqz file) should be submitted with the development application.
4.3.4 Preparation of a Detailed Stormwater Quality Management Plan
A DSQMP, based on the treatment train from the CSQMP or ‘Deemed to Comply Solution’, is to be submitted with an
operational works application. An initial assessment of the approved treatment train should be undertaken to confirm
its feasibility. If it is not feasible, a revised treatment train will be required with supporting information justifying why the
conceptual treatment train is not feasible. MUSIC modelling (or a revised ‘Deemed to Comply Solution’ if applicable) will
also be required to demonstrate the revised treatment train will meet the water quality objectives.
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When the final treatment train has been confirmed, detail design may be undertaken. Detailed design and reporting
should be in accordance with the design standards and Council adopted guidelines specified in Sections 7 and 8. The
following information should be included:
• a description of the stormwater treatment train;
• detailed engineering drawings of all stormwater treatment devices. These would typically include long and cross
sections and plan views of all treatment devices and any scour protection and sediment fore bays and outlet details;
• maintenance access details must be included on the drawings;
• detailed calculations for each treatment measure and completed copies of the applicable Design Calculation
Summary checklists from the Water Sensitive Urban Design Technical Design Guidelines for South East Queensland
(WSUD TDG);
• a copy of the relevant design assessment checklist from the WSUD TDG for each treatment measure;
• details of how all stormwater treatment devices will be protected during the construction and building phases based
on one of the four methods outlined in the Construction and Establishment Guidelines: Swales, Bioretention Systems
and Wetlands. Identify which method will be adopted for each treatment measure and include a copy of the relevant
step-by-step sequence and sign-off forms as an appendix to the report;
• where the stormwater treatment system is to be handed over to Council to maintain, identify the preferred asset
handover option (either bond or early handover with contribution) in accordance with the Logan City Council Water
Sensitive Urban Design Asset Handover Fact Sheet.
• an Operational Management and Maintenance Plan (OMMP) as a separable section of the DSQMP to demonstrate
the proposed treatment train can be practically maintained and to provide an outline of the proposed long term
operational management and maintenance requirements of the stormwater system on the site. The OMMP must
cover all aspects of the stormwater quality management system and include the following:
• aims and objectives of the stormwater quality management system;
• identify the person responsible for implementing the OMMP;
• a plan showing the location of the individual components of the system;
• manufacturer’s data and product information sheets for any proprietary products;
• location of inspection and monitoring points shown clearly on the plan;
• describe inspection/maintenance techniques and the associated rectification procedures;
• a schedule or timetable for the proposed regular inspection and monitoring of the devices;
• record keeping and reporting requirements (include the maintenance checklists located in the WSUD TDG); and
• review and updating requirements.
For privately maintained stormwater treatment systems, it will be a condition of the development approval that the
approved OMMP be implemented in perpetuity with regular inspection records maintained and made available to Council
upon request.
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5. Waterway stability design objective
5.1 Objective
The intent of this objective is to control the impacts of urban development on channel bed and bank erosion by limiting
changes in flow rate and flow duration within the receiving waterway.
The design objective is to limit the post-development peak one-year average recurrence interval (ARI) event discharge
within the receiving waterway to the pre-development peak one-year ARI event discharge (‘pre-development’ is defined in
Appendix B of Technical Note: Derivation of Design Objectives January 2009).
5.2 Applicability
This design objective only applies to assessable development where run-off from or within the site passes through or
drains to an unlined non-tidal watercourse or wetland. Where a receiving watercourse or wetland is degraded, compliance
with this objective is not required. For the purpose of these guidelines, a waterway is defined as degraded where:
• the proportion of impervious area within the catchment, prior to the proposed development, is greater than 30 per
cent, and the waterway stability objective has not been applied to any existing development within the catchment,
prior to the proposed development; or
• the waterway is designated as ‘highly disturbed’ in Schedule 1 of the Environmental Protection (Water) Policy
2009; or
• as otherwise determined by Council.
5.3 Demonstrating Compliance
Compliance with this design objective can be demonstrated by using one of the methods outlined in Appendix C of Water
Sensitive Urban Design: Developing Design Objectives for Urban Development in South East Queensland, Version 2,
November 2007, published by the SEQ Healthy Waterways Partnership.
6. Frequent Flow management design objective
6.1 Objective
To reduce the frequency of disturbance to aquatic ecosystems from urban development by managing the volume and
frequency of surface runoff during small rainfall events.
The design objective is to capture and manage from the proposed development:
• the first 10 mm of runoff from impervious surfaces where the total impervious surface is 40 per cent or less; or
• the first 15 mm of runoff from impervious surfaces where the total impervious surface is greater than 40 per cent.
Note: The capacity to capture runoff must be restored within 24 hours of the runoff event.
6.2 Applicability
This design objective only applies to assessable development where runoff from or within the site passes through or
drains to an unlined non-tidal watercourse or wetland. Where a receiving watercourse or wetland is degraded and Council
has deemed the watercourse or wetland to have no rehabilitation potential, compliance with this objective is not required.
For the purpose of these guidelines, a waterway is defined as degraded where:
• the proportion of impervious area within the catchment, prior to the proposed development, is greater than 30 per
cent; or
• the waterway is designated as ‘highly disturbed’ in Schedule 1 of the Environmental Protection (Water) Policy 2009;
or
• as otherwise determined by Council.
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Management of captured stormwater should include one or more of the following:
• reuse of stormwater (including collection and use of roof water);
• infiltration to native soils (where adverse impacts will not arise);
• diversion of surplus flows around sensitive downstream receiving environments; or
• evaporation of stormwater.
6.3 Demonstrating Compliance
Compliance with this objective can be demonstrated by providing a total stormwater capture volume in cubic metres (m3),
calculated as follows:
Capture volume (m3) = Impervious area (m2) x target design runoff capture depth
(mm/day) / 1000
The spatial distribution of the required capture volume may be adapted to suit individual site conditions, provided that the
required volume from all impervious areas is captured before leaving the site.
Since the objective requires that the capacity to capture this volume of runoff be available each day, the management
system (whether reuse, infiltration or diversion) must be capable of draining the captured stormwater within 24 hours.
Capturing the required volume of runoff will reduce pollutant load and simultaneously improve water quality. Therefore, it
may eliminate the need for separate additional storage to meet the objective for managing frequent flow if measures taken
to manage the quality of stormwater incorporate capturing this volume.
7. Design standards and specifications
All stormwater treatment measures must comply with the following design standards and specifications:
• bio-retention systems and constructed wetlands must be designed and located such that they maximise local and
regional flood immunity;
• stormwater treatment devices are not to be located in waterway or wetland buffers, unless the buffer is degraded to
the extent that placement of the device would result in an enhancement of the environmental values of the buffer;
• stormwater treatment devices are generally not accepted within the road reserve unless specific criteria are achieved
including widening of the road reserve by at least the total width of the device including batters, and hydraulics, safety,
services and alignments are not compromised (specific approval is required from Council’s Road and Infrastructure
Management Branch);
• treatment devices are generally not accepted within the road reserve unless specific criteria are achieved including
widening of the road reserve by at least the width of the device and hydraulics, safety, services and alignments are not
compromised (specific approval is required from Council’s Road and Infrastructure Management Branch);
• all treatment devices, (excluding any batters), must not be located above any in-ground services or infrastructure;
• Gross Pollutant Traps (GPT’s) are generally not accepted as part of the treatment train for assets to be handed over
to Council. Where gross pollutant and coarse sediment removal is required upstream of a Bioretention basin a coarse
sediment fore-bay or sediment basin should be incorporated into the design.
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8. Council ACCEPTED guidelines
All stormwater treatment measures should be planned, sized, modelled, designed and constructed in accordance with
the most current version of the following documents to the extent that they do not conflict with the design standards and
specifications outlined above.
Concept Design Guidelines for Water Sensitive Urban Design Version 1, Water by Design. South East Queensland Healthy
Waterways Partnership, Brisbane, March 2009
Water Sensitive Urban Design Technical Design Guidelines for South East Queensland, South East Queensland Healthy
Waterways Partnership 2006
Bioretention Technical Design Guidelines (Version 1), Water by Design (2012), Healthy Waterways Ltd, Brisbane
Deemed to Comply Solutions—Stormwater Quality Management (South East Queensland), Water by Design, South East
Queensland Healthy Waterways Partnership 2010
Construction and Establishment Guidelines: Swales, Bioretention Systems and Wetlands Version 1.1, Water by Design
2010
Water Sensitive Urban Design: Developing Design Objectives for Urban Development in South East Queensland, Version
2, South East Queensland Healthy Waterways Partnership, November 2007
Water Sensitive Urban Design Asset Handover Discussion Paper adopted by Council at its meeting of 31/05/2011 Minute
No 186/2011.
Asset Handover Guideline, Water by Design, 2010
MUSIC Modelling Guidelines, Water by Design
Queensland Division of the Institute of Public Works Engineering Australia, Standard Drawing numbers WSUD-001 to
WSUD-012