Knox City Council

Stormwater Drainage Guidelines

For Residential, Commercial, Industrial and

Broad Acre Subdivisional Developments

Dataworks Eng Templates Des044B May 2006

STORMWATER DRAINAGE GUIDELINES
FOR RESIDENTIAL, COMMERCIAL, INDUSTRIAL AND BROAD ACRE SUBDIVISIONAL DEVELOPMENTS

Table of Contents
1.0 Introduction 3

2.0 Pre-Development Discussions 3

2.1 Design Options 3

2.2 Existing Site Conditions 4

3.0 General Design Rules 4

4.0 Design Criteria 5

4.1 Hydrological Design 5

4.2 Recurrence Interval 5
4.3 Coefficient of Runoff and Time of Concentration 6
4.4 Hydraulic Analysis 6
4.5 Design Velocity 6
4.6 Ownership of Drainage 7

5.0 On-site Detention 7

5.1 Background 7
5.2 Design Criteria (Modified Swinburne Method) 7
5.3 Floor Levels 8
5.4 Information Required on Construction Plans 9

6.0 Engineering Drainage Construction Drawing Guidelines 9

6.1 Construction plans must be in accordance with… 9

6.2 Items to be shown on construction plans… 10
6.3 Containment of drainage from paved and roofed surfaces 10
6.4 Drainage construction requirements 11
1. Class of pipes allowed 11
2. Cover Details 12
3. Bedding 12
4. Backfill 12
5. Pit construction within developments 12
7.0 Drainage Design Guidelines for Broad Acre Subdivisions 13

7.1 Major Networks 13

7.2 Minor Networks 13

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STORMWATER DRAINAGE GUIDELINES
FOR RESIDENTIAL, COMMERCIAL, INDUSTRIAL AND BROAD ACRE SUBDIVISIONAL DEVELOPMENTS

1.0 INTRODUCTION

Knox City Council, as the Responsible Drainage Engineering Authority, has adopted
guidelines setting out drainage design engineering rules and conditions for residential,
commercial and industrial developments within the municipality. They are to be used as
guidelines by the applicant/developer for the above types of developments.

2.0 PRE-DEVELOPMENT DISCUSSIONS

Prior to submitting a Town Planning application, the applicant/developer should investigate

the existing drainage conditions on and in the vicinity of the subject site. It is anticipated
that this will reduce delays regarding stormwater drainage approvals.

It is important that prior to any development submission, the applicant/developer consult

Council’s Drainage Engineering Department ( 9298 8408), to determine the subject
site’s legal point of discharge, existing conditions and drainage requirements.

2.1 Design Options

In instances where there is no drainage available or the existing drains are inadequate,
Council may allow the following options to be provided by the applicant/developer, with
final approval to be given by Council:

• Construct a new outfall drain to the nearest suitable point of discharge at the
applicant’s cost.

• Upgrade a section of existing Council drainage system to accommodate the

proposed development. (Any possible future development is also to be considered).

• Design and install an adequate On Site Detention (OSD) system that will limit the
discharge rate from the proposed development to that determined by a weighted
coefficient of runoff of 0.4 as applied to the site.

• In some circumstances there may be an opportunity to use Water Sensitive Urban

Design (WSUD) practices as part of Council’s stormwater management plan.

• A combination of the above options.

• Council will require the applicant/developer to provide computations by a suitably

qualified engineering consultant who will determine the extent of any system
upgrade and/or the size of OSD system required to cater for the proposed
development.

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STORMWATER DRAINAGE GUIDELINES
FOR RESIDENTIAL, COMMERCIAL, INDUSTRIAL AND BROAD ACRE SUBDIVISIONAL DEVELOPMENTS

2.2 Existing Site Conditions

• Where the existing dwelling is to be retained as part of the unit development, the
applicant/developer shall determine and indicate on the plan the location of the existing
house drain and discharge point of the existing internal stormwater drainage system.

• Where existing drainage & sewerage easements are shown on the title, the
applicant/developer shall indicate on plan the exact location of any available assets
within the easement. This information is to be accompanied by pit/inspection opening
locations, size of pipe with depths and offset.

• All existing street features are to be accurately shown including driveways, pavements,
drainage pits, electricity poles, Telstra pits, sewerage manholes, trees etc.

• No permanent or habitable buildings are allowed to be built over Council easements.

However, in certain circumstances, removable structures may be allowed, subject to
consent from Council’s Building Department, prior to lodging an application with the
Planning Department.

3.0 GENERAL DESIGN RULES

• All storm and surface water shall be collected and discharged in a complete and
effective system of drains to be provided as directed by the responsible authority to an
underground pipe drain at the owners cost.

• Minimum size of a stormwater drainage outlet for a single dwelling is to be no less than
100mm diameter pipe.

• Minimum size of a common stormwater drainage pipe from a two dwelling development
is to be no less than 150mm in diameter. Upgrade of existing drainage and/or OSD
may be a condition of permit.

• Minimum size of a common stormwater drainage pipe for multi unit developments is
150mm diameter or greater, depending on the size of development and provided that
there is sufficient capacity downstream. Upgrade of existing drainage and/or OSD may
be a condition of permit.

• Size of a stormwater drainage outlet for commercial and industrial developments shall
be determined by computations provided by the developer’s engineering consultant
and will depend on the size of the development.

• Any on site drainage connecting into a Council or Melbourne Water drain must have
consent from the relevant authority.

• A Road Opening Permit needs to be obtained by the applicant prior to any construction
in a Council reserve or easement.

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STORMWATER DRAINAGE GUIDELINES
FOR RESIDENTIAL, COMMERCIAL, INDUSTRIAL AND BROAD ACRE SUBDIVISIONAL DEVELOPMENTS

• For all developments, the applicant/developer shall make provision for overland flows
through the subject site in the event of a blockage of the piped system or a storm
exceeding the capacity of the piped system.

• Any floor levels within the property adjacent to an overland flow path are to be
minimum 600mm above the lowest corner of property.

• Requirements such as use of litter traps may be imposed in some developments,

where deemed appropriate.

• Pipes within a drainage easement are to be no less than 150mm diameter in size.

• Pipes running longitudinally within the road reserve, are to be no less than 225mm
diameter in size.

• Pipes under road pavements are to be no less than 300mm diameter in size.

• Pipe materials, classifications and cover over pipe are to meet Council’s engineering
standards. Approved pipes shall be minimum Class 2 rubber ring jointed.

• Pipe types acceptable within road reserve are reinforced concrete, fibre reinforced
cement or UPVC pipes.

4.0 DESIGN CRITERIA

4.1 Hydrological Design

The Rational Method shall be used in calculating design peak flow rates through the
system.

Q = C I A / 360 (m3/s) or Q = C I A / 0.36 (l/s)

Q = peak flow rate (in litres per second or metres cubed per second)
C = runoff coefficient (based on fraction impervious)
A = area of catchment (Hectares)
I = rainfall intensity (mm/hr) (VicRoads road design manual, relevant intensity frequency
duration (IFD) charts – Melbourne area)

For large catchments, the times of concentration, overland flow determination and
coefficient of runoff shall be determined in accordance with the drainage chapter of
VicRoads Design Guidelines.

4.2 Recurrence Interval

• In residential areas the drainage system shall be designed for a 5 year Average
Recurrence Interval (ARI) or greater.

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STORMWATER DRAINAGE GUIDELINES
FOR RESIDENTIAL, COMMERCIAL, INDUSTRIAL AND BROAD ACRE SUBDIVISIONAL DEVELOPMENTS

• In commercial and industrial areas the drainage system shall be designed for a 10 year
ARI at least.

• For a main drain where the surcharge would seriously affect private property, the
drainage system shall be designed for a 10 year ARI.

• For major commercial areas e.g. Boronia or Bayswater, the drainage system and its
outfall shall be designed for a 25 year ARI.

4.3 Coefficient of Runoff and Time of Concentration

TYPE OF USE WEIGHTED Cr

Residential < 300m2 0.80
Residential > 300m2 0.60
Commercial 0.90
Industrial 0.90
Reserves < 1 Ha 0.35
Reserves > 1 Ha 0.45

For the purpose of calculating a weighted co-efficient of runoff for the design or analysis of
a drainage system the C pervious = 0.35 and C impervious = 0.90.

Minimum times of concentration:

Residential - 7 minutes
Low density - 9 minutes

Special consideration may be necessary for other buildings such as factories.

4.4 Hydraulic Analysis

Hydraulic grade line analysis to be undertaken to evaluate existing stormwater drainage

controlled or maintained by Council within the road reserve of property to determine design
levels of new pipes and pits.

4.5 Design Velocity

Minimum:

Pipe running half full or greater - 0.75 m/s

Pipe running less than half full - 1.00 m/s

Maximum:

• Pipe running full ≤ 5.5 m/s

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STORMWATER DRAINAGE GUIDELINES
FOR RESIDENTIAL, COMMERCIAL, INDUSTRIAL AND BROAD ACRE SUBDIVISIONAL DEVELOPMENTS

4.6 Ownership of Drainage

Subject to agreement by Council:

• Drainage constructed within easements or road reserves, will be handed over to

Council for the future maintenance and control after the completion of the contractor’s 3
months maintenance period to Council’s satisfaction.

• Drainage constructed outside an easement or within private / common property shall

remain the responsibility of the owner or body corporate for the future care and
maintenance of the drain.

5.0 ON-SITE DETENTION

Not to be sited on land to be maintained by Council e.g. road reserves, parks etc.

5.1 Background

Knox City Council has developed significantly in recent years. Some areas have been
densely developed and runoff flows exceed the capacity of existing Council stormwater
drainage pipes. Therefore, Council requires applicants/developers, to consider on-site
detention as one of the options for controlling the stormwater discharge increase that
results from most developments.

These guidelines require:

NO NET INCREASE IN STORMWATER RUNOFF.

PRE DEVELOPMENT DISCHARGE RATE = POST DEVELOPMENT DISCHARGE
RATE.

Applicants/developers are to provide on-site detention systems in order to restrict the rates
of flow from new developments to pre-development levels based on a weighted coefficient
of runoff of 0.4, or to a figure acceptable to Council that will not exceed the capacity of
existing drainage infrastructure.

5.2 Design Criteria (OS D4 Modified Swinburne Method)

Average Recurrence Interval:

• Detention System – to be designed for a 5 year ARI.
• Pre-development discharge – to be based on a 5 year ARI.
• Post-development discharge – to be designed for a 5 year ARI.

Coefficients of Runoff:
• Minimum for Permissible Site Discharge – 0.40.
• Development runoff coefficient – based on total anticipated impervious area.

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STORMWATER DRAINAGE GUIDELINES
FOR RESIDENTIAL, COMMERCIAL, INDUSTRIAL AND BROAD ACRE SUBDIVISIONAL DEVELOPMENTS

Time of Concentration:
• Development site, (Ts) – 5 minutes.
• Catchment, (Tc) – applicant to obtain from Council.
• Location within catchment, (Tso) – applicant to obtain from Council.

Rainfall Intensity (mm/hr):

• Relevant charts for Knox City Council – Adopt VicRoads standard (Melbourne chart).

Permissible Site Discharge:

• The discharge that would be generated by the development site assuming an average
coefficient of runoff of 0.40.

Orifice Size:
• The orifice diameter is to be determined by the Permissible Site Discharge applied to
the formula below. The restricting device must be placed so that the entire runoff from
all impervious areas within the development site passes through it. The orifice invert
must be set at the same level as the floor of the pit in which it is placed.

• Storage Volume shall be calculated by considering the anticipated inflow and

allowable outflow hydrographs applicable to the development site, to be sufficient for a
5 year ARI. (Use of OSD4 software is preferable.)

• For the analysis of an orifice the following formula is acceptable:

Q = Ao Cd √2gH

Q - discharge (m3/s)
Ao - area of orifice (m2)
g - acceleration due to gravity (m/s2)
H - head acting on orifice (m) i.e. above orifice centreline
Cd - coefficient of discharge is 0.6 for a square or rectangular outlet and
1.0 for a circular outlet.

• Orifice pits are preferable for discharge control instead of Phillips multi cell units.

5.3 Floor Levels

• Any floor levels of all buildings both existing and proposed are to be set at least
300mm above the water surface level of any above ground storage area or flood area.

• For any stormwater detention system a suitable overflow arrangement must be

provided to cater for higher intensity storms or in the event of an orifice blockage. The
overflow facility should be designed to pass the runoff generated by a 20-year average
recurrence interval storm for the particular development.

• Where it is intended to use a paved area for above ground storage, and also for
access or the parking of vehicles, the overflow should be positioned in such a way so
that the depth of water stored, does not exceed 200mm. It needs to be positioned so
that it does not obstruct pedestrian access to dwellings. Consideration should be

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STORMWATER DRAINAGE GUIDELINES
FOR RESIDENTIAL, COMMERCIAL, INDUSTRIAL AND BROAD ACRE SUBDIVISIONAL DEVELOPMENTS

made to ensure that all surcharge waters are directed away from dwellings and
garages.

5.4 Information Required on Construction Plans

Plans for detention systems shall include the following information as a minimum:

• Invert levels – all drains within the development site and outfall drainage external to the
site.
• Design surface levels adjacent to the device.
• Floor levels of all buildings both existing and proposed.
• Cross section details of the detention device.
• Existing surface levels of the development site.

Construction drawings, together with a set of drainage computations in accordance with

the above design criteria, are to be submitted to Council for approval prior to
commencement of any construction works.

• Ensure that the on site detention system is located within the area that is easily
accessible (i.e. common property within unit developments) and that the system is
always amenable to regular maintenance by the owner or the relevant body corporate.

• The location of overland flow paths is to be depicted on the layout drawing.

6.0 ENGINEERING DRAINAGE CONSTRUCTION DRAWING GUIDELINES

For further information on drainage design please contact the Drainage Engineer on 
9298 8408.

6.1 Engineering Drainage construction plans must be in accordance with:

(a) Approved development plan to Australian Height Datum (AHD);

(b) Town Planning Permit conditions;

(c) Council issued drainage direction;

(d) Melbourne Water approval is required, where any construction is proposed to be

adjoining or adjacent to any Melbourne Water declared drains or land subject to
inundation, e.g. overland flow paths, natural valleys, etc.

(e) VicRoads approval, where any construction is proposed involving access on to a Main
Road or Highway.

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STORMWATER DRAINAGE GUIDELINES
FOR RESIDENTIAL, COMMERCIAL, INDUSTRIAL AND BROAD ACRE SUBDIVISIONAL DEVELOPMENTS

6.2 The following items are to be shown on the Engineering Drainage

construction drawings:

Three sets of drawings are required for Town Planning assessment. Non compliance of
the required detail will delay the approval process.

General:

1. Lot No., boundary dimensions, easements – showing location of any assets e.g.
stormwater or sewerage.
2. Street names, north point. [North must be shown up the page].
3. Temporary or permanent bench marks. Location and level. [Level Datum to
A.H.D.]
4. Natural surface levels shown as contours.
5. Existing vehicle crossing (including size) and footpath.
6. Existing side entry pits in road reserve adjacent to property.
7. Existing drainage within property boundaries.
8. Existing service authority fixtures – poles, pits, hydrants, mains, etc.

Pavements:

1. Carriageway access widths, and car park set out details.

2. Design pavement contours to be shown, including design levels at all control points.
3. Pavement grades (maximum 1 in 8, minimum 1 in 200).
4. Pavement crossfalls (maximum 1 in 20, minimum 1 in 40).
5. All proposed floor levels.
6. Kerb details (if not standard).
7. Cross-section showing pavement makeup.
8. Expansion/contraction joints, type detailed and location specified.
9. For any alternative pavements, full details to be specified.
10. Soil analysis and pavement recommendation to be shown if alternative pavement
type intended (where applicable).
11. For pavement widening within road reserve, (e.g. deceleration lane, passing lane,
etc.) check requirements for pavement composition.
12. Access for disability – consideration shall be made for disability access in
accordance with the DDA (Disability Discrimination Act), i.e. maximum grade 1 in
14.

6.3 Drainage of all paved and roofed areas to be contained and controlled on
site:

1. Existing drainage levels.

2. Design drainage levels (to A.H.D.).
3. Downpipe locations and their connections to drainage system.
4. Pipe sizes, types and gradients to be specified.
5. Pit sizes and types to be specified.
6. For industrial, or commercial developments, the pavement drainage is to be via
kerb and channel and side entry pits.
7. Trench gratings in accordance with design loads.

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STORMWATER DRAINAGE GUIDELINES
FOR RESIDENTIAL, COMMERCIAL, INDUSTRIAL AND BROAD ACRE SUBDIVISIONAL DEVELOPMENTS

8. The drainage collection system for each unit on the site shall be independent of the
others with a single connection point to the central or common system.
9. Maximum distance between pits – 30 metres.
10. Where construction is proposed over an existing Council drain or easement,
application must be made as soon as possible to the Building Surveyor, where
structural building works are concerned.
11. Storm Recurrence Interval – 10 year return period to be used for industrial and
commercial developments, and 5 years for residential.
12. Method of providing water proofing to the buildings (where appropriate) to be
detailed. For example, where a wall is to act as a retaining wall, consideration
should be given to providing adequate subsoil drainage and a suitable tanking
membrane.

6.4 Industrial, Commercial and Multi-Unit Development – Drainage

Construction Requirements

1. Class of pipes allowed:

(a) Concrete Pipes

Shall conform to AS 1342-1973 “Precast Concrete Drainage Pipes” and its

amendments. All pipes designated as R.C. pipe on the drawings shall be Class 2
pipe with spigot and socket rubber ring joints.

(b) Fibre Reinforced Cement Pipes (F.R.C.).

All Fibre Reinforced Cement Pipes shall conform to AS 1342-1973 “Precast

Concrete Drainage Pipes”. All pipes designated as F.R.C. pipe on the drawings
shall be Class 2 pipe with Adcol “V” ring joints.

(c) PVC
- Within property Installation of P.V.C. pipes shall be specified as U.P.V.C.
sewer quality or U.P.V.C. heavy duty stormwater, depending on application.
Jointing of pipes shall be either:
i) solvent welded; or
ii) rubber ring joints.
All jointing procedures to conform with AS 2032 Part 3.
The installation of U.P.V.C. pipes to be in accordance with Part 7 of AS
2032.
- Within road reserve All U.P.V.C. pipe shall conform to AS 1260-1974 Parts
1-5 “Unplasticised P.V.C. (U.P.V.C.) pipes and fittings for sewerage
applications.”
All pipes designated as U.P.V.C. pipe on the drawings shall be Class S.H.
Sewer Grade.
- On-site detention storage polyethelene pipe as supplied by Caliber
Pipelines (formerly RibLoc Australia) or Blackmax supplied by Iplex Pipelines
Australia Pty Ltd.

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 STORMWATER DRAINAGE GUIDELINES
FOR RESIDENTIAL, COMMERCIAL, INDUSTRIAL AND BROAD ACRE SUBDIVISIONAL DEVELOPMENTS

2. Cover Details

Cover Requirement Class Pipe Required

Application RCP/FRC UPVC Minimum RCP/FR UPVC
Pipe C
Diameter
Not subject to vehicular Heavy Duty Storm
loading 150mm 300mm 90mm 2 Water
Traffic Areas:
Not in Road Reserve
Refer Notes 1 2

(i) within road reserve Sewer Quality – SH

(not in road 500mm 500mm 225mm 2
formation) Sewer Quality – SH

600mm 600mm 150mm 2

(ii) in sealed roadway
Sewer Quality - SH
Under building slabs 1 600mm 150mm 2

Notes:

(1) Cover to be minimum of 150mm below underside of slab or 500mm below

finished level of sealed pavements.

(2) If cover is not obtainable, then pipe in areas not subject to construction
vehicle loading may be encased in 100mm of concrete.

(3) Whole drain to be encased in 100mm of concrete.

3. Bedding

All drains to be laid in fine crushed rock – minimum of 50mm depth.

4. Backfill

All drains to be backfilled with suitable material properly compacted, for sealed pavements
trenches are to be backfilled with 20mm Class 2 crushed rock. Under slabs, it is preferred
that where drains are laid close to the surface, the backfill be crushed rock.

5. Pit construction within developments

Refer to Council Standard Drawings for pit construction within the road reserve.

Pits to be constructed in concrete.

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STORMWATER DRAINAGE GUIDELINES
FOR RESIDENTIAL, COMMERCIAL, INDUSTRIAL AND BROAD ACRE SUBDIVISIONAL DEVELOPMENTS

Sizes: Junction pits up to 0.5 m deep minimum 500 mm x 500 mm

Junction pits 0.5 to 0.8 m deep minimum 600 mm x 600 mm
Junction pits greater than 0.8 m deep minimum 900 mm x 600 mm
Side entry pits up to 1.5 m deep minimum 1000 mm x 600 mm
Side entry pits greater than 1.5 m deep minimum 1000 mm x 900 mm

Note: Polycrete pits or approved equivalent may be acceptable at the discretion of

Council’s Representative.

Trench Grates – minimum width of 225mm.

7.0 DRAINAGE DESIGN GUIDELINES FOR BROAD ACRE SUBDIVISIONS

7.1 Major Networks

• Return period is 100 years.

• Flow paths need to be demonstrated.
• Flow volumes need to be estimated.
• Flood levels need to be estimated in order to prevent any blocks from
inundation.

7.2 Minor Networks

7.2.1 Return Period:

Industrial Subdivisions - 10 years

Residential Subdivisions - 5 years

7.2.2 Runoff Coefficients:

Industrial - 0.90
Shop sites - 0.90
Residential < 300m2 - 0.80
Residential > 300m2 - 0.60
Low Density - 0.45
Reserves < 1 Ha - 0.35
Reserves > 1 Ha - 0.45

7.2.3 Rainfall Intensities:

Knox City Council rainfall intensities are to be used – Melbourne Area
acceptable.

7.2.4 Minimum Times of Concentration:

Residential - 7 minutes
Low Density - 9 minutes

7.2.5 Manning’s n, sewered & unsewered - 0.013

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STORMWATER DRAINAGE GUIDELINES
FOR RESIDENTIAL, COMMERCIAL, INDUSTRIAL AND BROAD ACRE SUBDIVISIONAL DEVELOPMENTS

7.2.6 Design needs to cater for all external catchments. Tree reserves should be included
in the catchment area.

7.2.7 Provide drainage computations that show pipes to be of sufficient capacity.

7.2.8 Check if existing properties upstream have existing drains.

7.2.9 Check if there is any outfall drainage available. If so check if the consent is
required from:

• Affected landowners.
• Melbourne Water.

7.2.10 If any drainage outfall discharges into another property you need to:

• Ensure that an easement exists.

• Require permission from adjoining owner to enter, and carry out works.

7.2.11 Depth of open outlet drains is to be no more than 1.5m maximum, and side
slopes to be no steeper than 1 in 3.

7.2.12 Check whether catch or cut off drains are required to protect houses from sheet
flow from undeveloped neighbouring properties.

7.2.13 Velocity in all pipes needs to be greater or equal to 1 m/s, in order to enable
self-cleansing.

7.2.14 Minimum drop through pits is 50mm. Larger drops may be required if head
losses are high.

7.2.15 Check if any pipe outlets to lakes or dams are submerged. If so check if
backing up in pipelines will occur.

7.2.16 No bends in drainage lines larger than 90° are allowed. Also avoid opposing
pipes.

Pipes that are 525mm in diameter and larger, can have bends less than 45° as
per manufacturers’ recommendations.

7.2.17 Provide correct drainage computations. Make sure that the sub-areas are
draining as per detail and that they are correct in size & time.

7.2.18 Aim for a layout that provides for the drainage of each property at the lowest
corner.

7.2.19 All house drain connections in the street are to be located 6 metres from the
side boundary to allow for vehicle crossing alterations.

7.2.20 Consider Water Sensitive Urban Drainage Design methods and options.

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STORMWATER DRAINAGE GUIDELINES
FOR RESIDENTIAL, COMMERCIAL, INDUSTRIAL AND BROAD ACRE SUBDIVISIONAL DEVELOPMENTS

7.2.21 All pits are to be a minimum of 7m from the side boundaries, except where
required to cater for easement drains.

7.2.22 Drainage pipes that are parallel to the road should be laid on the high side for
practical purposes.

7.2.23 Ensure that there are no Grating Pits or SEP’s between T.P.’s in kerb returns
(only permitted in exceptional cases).

7.2.24 Minimum pipe sizes:

• General 225mm
• Outlet from SEP 225mm
• Under road pavement 300mm

7.2.25 Pipes should not decrease in size downstream.

7.2.26 Minimum cover is:

• 500mm in easements
• 500mm in nature strips
• 225mm under base course

7.2.27 Pipes up to and including 600mm diameter are to be RRJ, Class 2 RCP. (Pipes
in easements, of 150 and 225mm Dia, may be Class 12 PVC, UPVC SHGrade).

7.2.28 Rubber ring joints need to be provided for large diameter pipes on curves or
where there will be heading in pipe.

7.2.29 Easement drains should be located to provide 500mm clearance from either
side of easement.

7.2.30 Anchor blocks are required on all pipes with a slope greater than 1 in 10, at 10
metre intervals.

7.2.31 For pipes greater than 1000mm, a separate drain is required for individual
house drains.

7.2.32 Maximum spacing of side entry pits along kerb and channel is 80m (provided
grade is above 1 % when properties drain to kerb and channel).

7.2.33 Maximum spacing of pits for easement drains is 60m (for maintenance
reasons).

7.2.34 Invert level of property inlets to be minimum of 500mm below finished natural
surface.

7.2.35 Side entry or Grating pits are required on all returns to prevent water flowing
around the return.

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STORMWATER DRAINAGE GUIDELINES
FOR RESIDENTIAL, COMMERCIAL, INDUSTRIAL AND BROAD ACRE SUBDIVISIONAL DEVELOPMENTS

7.2.36 Grating pits, type S-120 series to be shown on all type S-301 series kerb &
channel.

7.2.37 Pits deeper than 2.5m required gatic covers or as specified.

7.2.38 Maximum depth of 600 x 600 easement pits to be 800mm.

7.2.39 Minimum depth of side entry pits to be 900 + D/2 to facilitate connection of A.G.
drains.

7.2.40 Pit schedule is required with the appropriate pit types and correct sizes shown.

7.2.41 Pipes laid around road curves are to be laid straight between pits. Curved
pipeline are allowed using RRJ pipes within the radius and deflection limits
specified by the manufacturer.

7.2.42 Pipes under pavements, parking bays, etc and where side of trench comes
within 150mm of back of kerb, must be backfilled with crushed rock. Such
backfilling must be shown on long sections.

7.2.43 Pit covers to be “Terra Firma” or similar in road reserves and drainage
easements unless otherwise specified.

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