Edition: September 2011
CONTENTS
1.
2.
3.
4.
5.
6.
7.
8.
9.
General
References
Design Requirements
Design Procedures
Materials
Temporary Drainage
Environmental Requirements
Approval of Drainage Design
Records
CSTR: Part D022 Design – Roadworks Drainage
PART D022
DESIGN – ROADWORKS DRAINAGE
1. GENERAL
This Part specifies the requirements for the design of drainage for roadworks, including stormwater drainage elements, sedimentation control devices and temporary drainage structures.
"Drainage Authorities" means the local Council(s) and any relevant catchment management authority.
2. REFERENCES
Unless specified otherwise, all design shall be undertaken in accordance with the following:
1.
DPTI: Road Design Standards and Guidelines (Refer http://www.dpti.sa.gov.au/standards ).
2.
Australian Rainfall and Runoff (ARR).
3.
Austroads Waterway Design Guide.
4.
Environmental Protection Authority "Stormwater Pollution Prevention – Code of Practice for Local, State and Federal Government".
5.
Environmental Protection Authority "Stormwater Pollution Prevention – Code of Practice for the Building and Construction Industry".
6.
Protecting Waterways Manual (Transport SA 2002)
7.
EPA Environment Protection Water Quality Policy (2003).
8.
Australian Runoff Quality, A Guide to Water Sensitive Urban Design, Engineers Australia (2006).
10. Planning and Local Government WSUD Technical Manual for Greater Adelaide
(Refer http://www.planning.sa.gov.au/go/wsud ).
3.
3.1
DESIGN REQUIREMENTS
Design Life
The Contractor shall design assets for the following minimum design life:
ELEMENT
Scour protection
DESIGN LIFE
(YEARS)
50
100 Inaccessible drainage elements
Drainage elements that are accessible for refurbishment, except for water quality elements
Water quality elements
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Edition: September 2011 CSTR: Part D022 Design – Roadworks Drainage
“Water quality elements” includes sedimentation / retention / detention basins and ponds.
3.2 Design of the Drainage System
The Contractor shall obtain all necessary approvals relating to the drainage design from the Drainage Authorities
(refer to D020).
The design flows and detailed hydraulic design of the system shall take into account the constraints imposed by existing or proposed drainage systems and Utility Services.
Unless adversely affected or constrained by existing or proposed drainage systems, drainage systems (including culverts, drainage networks, kerb and channel and open drains) shall cater for the design storm event listed in
Clause 3.6 "Pavement Drainage". The system shall have sufficient capacity to accommodate the design drainage flow in accordance with the drainage condition requirements and without causing damage or nuisance to surrounding landowners and properties.
Discharge from the works site to any downstream pipe or channel system shall not increase flows in that system to the extent that the design standard of the existing system is compromised.
Existing drainage catchments and flow patterns shall be maintained where practicable and drainage flows shall not cause damage or nuisance to surrounding landowners and properties. The Contractor shall not permit re-direction, concentration or diversion of drainage flows for the Works except with the written consent of the responsible drainage authority and any other affected parties.
No runoff from any part of the Works shall be discharged out of any road corridor unless it is in an underground or surface drainage system, including underground flows.
All specified or calculated waterway areas shall be maintained if embankment or foundation settlement occurs.
3.3 Average Recurrence Intervals
The following minimum design average recurrence intervals (ARIs) shall be applied to the drainage design:
ELEMENT DESIGN ARI
Channels and open drains
Gutter flow width
Piped system (including pits)
5 years
5 years
5 years
Major storm for the purpose of checking that properties are not adversely affected
100 years.
3.4 Hydrology and Hydraulic Calculations
Hydrology and Hydraulic Calculations shall be undertaken in accordance with the following:
(a) Determination of catchment areas shall allow for the road pavement, the remainder of any road corridor and any area external to the corridor;
(b) Runoff coefficients assigned to different catchment areas shall be in accordance with recognised reference sources;
(c) Design rainfall intensities shall be calculated in accordance with the procedures outlined in Australian
Rainfall and Runoff;
(d) An Antecedent Moisture Condition (AMC) of 2 shall be used in the DRAINS model, if this model is used.
Otherwise it shall be assumed that the soil is dry at the start of the design storm event.
(e) Recognised drainage design programs shall be used. Adopted design flows shall be derived from the storm that produces the largest peak flow; and
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Edition: September 2011 CSTR: Part D022 Design – Roadworks Drainage
(f) Hydraulic designs shall calculate hydraulic grade lines for both main and lateral systems and include allowance for pressure losses through junction boxes and other loss producing elements in accordance with recognised reference sources.
3.5 Drainage System Elements
The Contractor shall ensure the correct drainage system elements (including pits, kerb & gutter, driveway crossover, kerb-outlet, etc) are used as appropriate for each road classification and road maintainer DPTI or relevant Council as the case warrants.
Drainage system elements including pits, culverts, sedimentation basins and subsurface drain outlets shall be readily accessible for cleaning and unblocking and the whole drainage system shall be designed and constructed so as to minimise maintenance.
Culverts shall be self-cleaning and shall be of a depth that provides for the connection of any subsoil drainage systems.
The minimum allowable slope for kerbing, pipes and culverts is 0.2%. Grades flatter than 0.2% may only be used with the prior approval of the Principal.
The desirable grade for table drains and swales is 0.4% to 0.6%. The minimum allowable grade is 0.3%. The 1 in
10 year ARI flow velocity should not exceed 1m/sec for unlined and vegetated systems. The drains shall not be V shaped.
Culverts shall not intrude into pavement layers without the prior approval of the Principal.
Wherever practicable, ends of culverts shall be located beyond the clear zone for the respective section of road. Any pit or culvert end within the clear zone shall be made trafficable, or if this is not practicable, protective treatment shall be installed.
The drainage design shall include the design of catch drains at the top of batters to prevent runoff from eroding cutting faces, The catch drains shall be lined with an impervious lining if necessary to prevent piping failure of the batter slopes. The drains shall not be V shaped.
All detention basins and stormwater treatment ponds shall contain an impervious lining.
3.6 Pavement Drainage
The pavement drainage design shall incorporate the following:
(a) Gutter flow widths shall allow minimum allowable trafficable lane width during the design event;
(b) A minimum freeboard of 200 mm is required between design water levels and gutter levels at entry pits;
(c) The specified road pavement drainage standard does not preclude the Drainage Authorities requiring a higher standard if parts of the drainage system that is their responsibility requires alteration, under grounding and/or other changes due to the proposed roadworks;
(d) A 1 in 100 year ARI flood event shall be modelled and a check made of flow levels to ensure that flooding of property is avoided;
(e) Runoff from ramps or turning roadways shall not flow beyond noses and across the main carriageway for a
1 in 2 year Average Recurrence Interval storm event;
(f) Runoff shall not be discharged down any batter greater than 1m in height with a slope exceeding 1:4 unless contained within a formal drainage system;
(g) Aquaplaning potential shall be minimised ;
(h) Concentrations of water and long surface drainage paths on pavement crossfall and superelevation transition areas shall be prevented; and
(i) Runoff from bridge decks shall be collected and discharged into the road drainage system.
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3.7 Scour Protection
Scour protection shall be provided at any area susceptible to scouring, such as batters, bridge abutments, verge drains, culvert inlets and outlets, pipe outlets, and .where changes are required along watercourses where there may be a risk of erosion. Scour protection shall prevent scour for the design drainage flow. Techniques shall be appropriately selected and designed to suit the application and performance requirements.
Where dispersive soils (Soils having Emerson Class 1 or 2 in accordance with AS 1289.3.8.1-2006) are exposed a minimum of 100mm of non-dispersive topsoil shall be placed before revegetation (Refer to D037 for revegetation requirements) or the placement of any erosion control measures.
3.8 Water Quality
Design of the stormwater network shall include management of stormwater quality to reduce and manage pollutants from the stormwater network and operation of the roadway.
The design of the stormwater drainage network shall ensure stormwater quality at the Southern Expressway, prior to discharging into the local waterways, is as a minimum equivalent to the existing (pre-construction) water quality levels.
The design of the stormwater network shall achieve the water quality targets as detailed in D020 Design –
Environmental.
The design of the stormwater network shall include:
(a) water quality analysis that demonstrate the quality of the stormwater including water quality modelling
(MUSIC or other approved modelling package) where water quality targets have been set for the project.
Where the target water quality levels cannot be achieved the Contractor shall detail the options investigated to demonstrate what the target levels cannot be achieved;
(b) at a minimum a range of appropriate features, structures (gross pollutant traps), modifications to existing sediment basins and wetlands, to manage stormwater quality;
(c) consideration of maintenance of any stormwater quality features, measures and structures;
(d) supporting information detailing the design assessment as part of the design report;
(e) measures to prevent inflow of saline ground water into the drainage channels (which could affect vegetation in swale and channels); and
Where appropriate, the design shall consider:
(f) detaining and slowing the conveyance of stormwater through the treatment and vegetated systems, and interception drains;
(g) use vegetation and landscaping to filter and treat stormwater;
(h) integration of stormwater management into the landscaping through the implementation of sustainable management techniques;
(i) water efficient landscaping and the use of local indigenous vegetation species for all stormwater treatment systems;
(j) protection of the aquatic environments such as watercourse, groundwater quality and their associated values;
(k) protection and enhancement of recreational, social, and cultural values;
(l) improved biodiversity, ecological and habitat outcomes through the implementation of sustainable stormwater management techniques; and
(m) the achievement a design that facilitates community and institutional education, expectations, standards and demonstration of current best practice in stormwater management.
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4. DESIGN PROCEDURES
Drainage systems shall be designed using recognised design programs. The design program shall:
(a) model pit entry capacity;
(b) model bypass flow to next pit;
(c) model detention basins if utilised;
(d) model overland flow times;
(e) model infiltration rates;
(f) model pollutants; and
(g) provide a routed reach outlet hydrograph.
Pipes that are running full shall be analysed to determine their hydraulic performance, including details on flow types and hydraulic grade lines. Pit entry and exit losses shall be considered.
Hydrologic and hydraulic designs must be independently certified in accordance with Part 706 "Proof Engineering".
5. MATERIALS
Culverts shall comply with the following:
(a) unless approved otherwise by the Principal and the Drainage Authorities, pipe culverts shall be either concrete, fibre cement or Black Max;
(b) box culverts shall be concrete;
(c) culvert classifications and installations shall be as required by the Australian Standard relevant to the culvert material used;
(d) the diameter of pipe culverts placed under the pavement shall not be less than 375 mm;
(e) the height of box culverts placed under the pavement shall not be less than 300 mm and shall be 375 mm or greater whenever practicable; and
(f) pipe loadings for pipe class selection shall be the more critical of expected construction equipment loading or traffic loading.
The following materials shall not be used for drainage purposes:
(a) metal culverts to AS 2041; and
(b) plastic pipes (except Black Max).
6. TEMPORARY DRAINAGE
Temporary drainage systems used for the Works shall be designed for a 2 year Average Recurrence Interval. The temporary drainage system shall satisfy the requirements of the Drainage Authorities.
7. ENVIRONMENTAL REQUIREMENTS
Further to Clause 155 "Environmental Protection Issues", the Contractor shall design any measures necessary (either temporary or permanent) to comply with the requirements of the Soil Erosion and Drainage Management Plan
(SEDMP).
In addition to the water quality requirements of this part, the design of the stormwater network shall include, management of chemical or flammable goods or liquids including emergency response and capture from the road corridor.
As part of the design report the Contractor shall prepare an Emergency Response plan detailing the measures to protect water quality and soil contamination in the event of a spill.
The design vehicle for spills for chemical or flammable goods or liquids shall be a fully laden Semi Trailer.
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8. APPROVAL OF DRAINAGE DESIGN
The design and hydraulic modelling of any modifications to the existing drainage network including any basins / wetlands, shall be in consultation with the relevant Council(s), or approval authority.
The Contractor shall obtain and provide written approval of the design and hydraulic modelling of any modification to the existing drainage network from the Principal and relevant Council(s), or approval authority.
8. RECORDS
The following records shall be provided to the Principal:
Drawings
The drawings described in the DPTI: Road Design Standards and Guidelines and Part D010.
As constructed drawings.
Drawing of any temporary drainage and/or sedimentation control devices required to comply with the
SEDMP.
Reports
Drainage calculations in relation to drainage system capacity.
Design reports describing:
(a) the management of the roadway drainage
(b) water sensitive urban design elements and water quality analysis; and
(c) assessment of hydraulic grade lines, design flood events, stream velocities and scour protection.
Copies of all electronic input and output files applicable to the final design.
Stormwater Treatment Infrastructure (STI)
The contractor shall submit information, in the form of proformas, which record physical details and maintenance requirements for any stormwater treatment devices that are associated with the works.
The Contractor shall update the Stormwater Treatment Infrastructure (STI) manual by completing a "New
STI (Location) Proforma" (Refer to Appendix 20.2) and a "New STI (Type) Proforma" if not already included in the manual (Appendix 20.3).
Implementation Records
Approvals from the Drainage Authorities (to be submitted prior to the conclusion of the relevant design stage).
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