TRENCHING AND CONDUIT STANDARD FOR …tkne.net/downloads/power/cabels3/Trenching for underground cables.pdf · This Technical Standard is based on the Electricity (General) Regulations

5

E T S A U t i l i t i e s

D e l i v e r i n g e n e r g y t o S o u t h A u s t r a l i a n s

ETSA Utilities, ABN 13 332 330 749, a partnership of:

CKI Utilities Development Limited,ABN 65 090 718 880.

HEI Utilities Development Limited,ABN 82 090 718 951.

CKI Utilities Holdings Limited,ABN 54 091 142 380.

HEI Utilities Holdings Limited,ABN 50 091 142 362.

CKI/HEI Utilities Distribution Limited,ABN 19 091 143 038.

each incorporated in The Bahamas

Copyright 2004

TRENCHING AND CONDUIT STANDARD

FOR

UNDERGROUND CABLE NETWORKS

Technical Standard TS-085

Issued: April 2005

Trenching & Conduit Technical Standard TS - 085

Issued: April 05 TS -085 Authorised: J Ali 11/04/05 Page:1 of 23

1.0 DEFINITIONS The term "ETSA Utilities" means :- ETSA Utilities, ABN 13 332 330 749, a partnership of: CKI Utilities Development Limited, ABN 65 090 718 880. HEI Utilities Development Limited, ABN 82 090 718 951. CKI Utilities Holdings Limited, ABN 54 091 142 380. HEI Utilities Holdings Limited, ABN 50 091 142 362. CKI/HEI Utilities Distribution Limited, ABN 19 091 143 038. each incorporated in The Bahamas 1 Anzac Highway, Keswick, South Australia, 5035.

2.0 BACKGROUND

The responsibility for the installation of a trench for the installation of ETSA Utilities infrastructure can be: • The developer for land developments or a customer for network extensions and

alterations to the ETSA electrical network. • Council for Power Line Environment Committee (PLEC) projects. • ETSA for capital works and, under specific arrangements, some customer works.

ETSA Utilities may agree to provide a quotation for the installation of a trench on behalf of a customer or a developer. For access to the list of Civil Contractors utilised by ETSA Utilities refer to section 15.0. This Technical Standard is based on the Electricity (General) Regulations 1997. For any situation that is not covered by this Technical Standard, the requirements of AS/NZS 3000-2000 shall apply. Trenching needs to be undertaken in a workman-like manner and must meet the requirements in TS – 085 and any other relevant specification. A “Civil Works Compliance” form is required prior to any Network connection. Refer to section 14.0 for further information. Section 5.0 of the ETSA Utilities Terms and Conditions for External Contractor Construction (refer to sect 15.0 for access) details the customer/developer’s obligations. The trench is a critical and integral part of the electrical installation. ETSA cables are covered in a soft layer of polyethylene which is very easily damaged. A contractor should not work near any live electrical cables. Dial Before You Dig should be contacted on telephone number 1100 to verify the location of ETSA and other infrastructure prior to the commencement of any civil works. An access permit may be required if any electrical cables are in close proximity. A contractor can contact the Network Access Officer on 84044119 for further information.



A contractor should not work in the area where there is electrical infrastructure, even if the asset is de-energised without a high degree of due care as the cables can be easily damaged. To reduce the severity of damage to the outer sheath, all contractors who have to work in the area of the electrical infrastructure MUST utilise a safe edge (blunt nosed) shovel. This style shovel minimises cable damage if a contractor inadvertently comes in contact with a cable. Any damage to ETSA infrastructure will be at the cost of the responsible party. If any party is aware of any damage to the electrical infrastructure, ETSA or the electrical contractor undertaking an installation should be notified at the earliest opportunity. Early notice may reduce future repair costs. The trench containing the electrical works is a component of the asset inspection process and it is the responsibility of the developer/customer to ensure that the trench meets the specification. An ETSA Asset Compliance Officer may inspect the trench and any requirement for remedial work to a trench to ensure it satisfies this Technical Standard and any associated specification will be at the developer/customer’s cost. If there are any queries on this Technical Standard (TS –085) the Project Officer responsible for your project should be contacted.

3.0 RETAINING WALLS

A transformer can weigh from 2.0 tonnes for a 150 kVA transformer up to 6.2 tonnes for a 2000 kVA transformer. There may be a requirement to establish a retaining wall to ensure the transformer has a stable footing. The involvement of a Certified Engineer may be required to verify the adequacy of any retaining wall installation. Council approval may also be required. ETSA Utilities reserves the right to request engineering calculations for any retaining wall.

A retaining wall for a Padmounted Transformer or a Switching Cubicle will normally be installed in any location where there is a change in the natural (unchanged) ground level of 300 mm or more within two metres of the standard easement boundary for the electrical equipment.

Any retaining wall above 1.0 metre in height will require engineering confirmation of the design and Council approval.

A Retaining wall must be completed prior to the installation of a padmounted transformer and a switching cubicle.

The retaining wall should ideally be positioned at the extremity of the ETSA Utilities easement and should not encroach into the area occupied by the transformer or switching cubicle. The easement shall be of such a size that the retaining wall is constructed entirely within the easement (see Figure 1). Where the wall is placed beyond the standard easement, the easement must be extended to include the area occupied by the retaining wall.

In situations where a retaining wall is required for the retainment of fill material, the easement boundary is to be extended by 1.0 metre to allow the retaining wall to be constructed 1.0 metre inside the easement boundary.



The retaining wall and backfill must be designed to drain the area behind the wall completely and to continue to do so indefinitely without blockage, so that hydrostatic pressure is not exerted on the wall at any time.

Retaining walls shall be constructed of concrete masonry materials. If interlocking style blocks are utilised, they must be of a pinned or socket and nib type. The two top courses shall pinned and glued with an epoxy style resin and the top course shall consist of a glued top capping

Open style interlocking blocks may be acceptable provided the soil is retained. The use of Geo cloth type material may also be acceptable. To ensure the material to be utilised for a retaining wall will be acceptable to ETSA Utilities, please contact your ETSA Utilities Project Officer prior to installation. This style of retaining wall construction has the potential to require an easement larger than standard.

ETSA Utilities will consider a submission from a certified engineer to a variation to the construction material utilised for a retaining wall as described in this section.

Material to be retained shall be classified in one of the 3 types listed below: • Coarse grained soil without admixture of fine soil particles. Very

permeable (clean sand or gravel) • Coarse grained soil of low permeability due to admixture of particles of

silt size. • Residual soil with stones, fine silty sand and granular materials with

conspicuous clay content.

Materials not acceptable include very soft or soft clay, organic silt or silty clays, and medium or stiff clay.

Weep holes shall be provided in the retaining wall at the lowest points. An open drain shall be provided to remove water from the area of the toe of the wall. A more effective system of drainage consists of a continuous agricultural pipe located at the base of all retaining walls and be surrounded by gravel or crushed stone with a continuous vertical layer of granule material at least 300 mm thick covering the rear face of the wall area.

Operating areaRefer to TS - 102

TRANSFORMERBoundary of PublicArea if appropriate.

Easement to beextended toinclude the areaoccupied by theretaining wall ifrequired.

Area for ETSAEquipment (onstandardeasement, 3.5 x2.5 m).

RETAINING WALL Figure 1

Retaining Wall

ORSWITCHING CUBICLE



RETAINING WALL - FILL Figure 2Retainingwall

ETSATransformer/switching cubicle

300mmminm

Granulated materialbehind all retainingwall sections

Continuous agriculturalpipe the length all retainingwall sections plus externalweep holes on the lowestsection of the retaining

llGround level

NoteRetaining wall to bebuilt up to the heightof the base

Weep hole

Suitable retainingfill

Ground level

300mmWeep hole

Ag pipe to exit at thefront of the retaining wall

Ground level

Continuous agriculturalpipe the length all retainingwall sections plus externalweep holes on the lowestsection of the retaining

ll

RETAINING WALL - CUT Figure 3

Retaining WallWith 100mm lipabove groundlevel

ETSATransformer/switching cubicle

Groundlevel

PreferredEasement

Dispensation for the installation of a retaining wall can be granted by the relevant regional Network Manager when the following can be verified;

• The short and long term stability of the transformer will not be compromised. • The easement site will not be impacted by erosion run off, i.e. it can be

demonstrated that the site adjacent to the easement is well consolidated and /or there is other means of retainment or removal of any run off material.

4.0 TRENCHING

4.1 General

When conduits or cables are to be installed, the trench shall be as straight as possible with a firm and smooth base. The installation of multiple conduits requires a minimum separation of 25mm in all directions between ETSA conduits and ETSA cables to ensure the bedding sand fully encompasses the conduit at the time of back filling. This will reduce future compaction issues.



There shall be a minimum separation of 50mm between direct laid ETSA cable circuits. The greater the cable circuit separation, the greater the current carrying capacity of the electrical cable. If the trench width is such that the minimum separation can be increased and the 50mm clearance to the trench wall is met, then the separation should be increased. From time to time there may be a requirement for a specific separation that is greater then the minimum. Separation from a trench wall to any ETSA infrastructure will normally be a minimum of 50mm. This is to reduce any damage to electrical infrastructure from sharp edges, stones, etc. Under some circumstances ETSA may approve a lesser dimension if it can be verified the trench edge is such that it will not damage the installed cables or if the installed conduit is medium or heavy duty. Dimensions for ETSA infrastructure in this standard are the minimum except where shown.

The maximum depth of any length of trench or conduit should not be greater then 1.5 metres unless ETSA has approved a section of trench/ conduit installation at a greater a depth. Any depth beyond this will be labelled an excavation and may require shoring to be installed. Refer to the Occupational Health, Safety & Welfare Regulations 1995.

The Trench shall be located, when practicable, in accordance the publication “A Code for the Placement of Infrastructure Services in New and Existing Streets” (Services in Streets Code) prepared by the Public Utilities Advisory Committee (PUACC) and available from the Local Government Association.

All variations to the Construction drawing must be noted by the installation contractor and included on the “As Constructed” ETSA drawing. 4.2 Road Reserves and Road Crossings The minimum cover under a carriageway shall be 750mm. A Transport SA road has specific requirements and these are detailed in section 4.3 All cables under carriageways shall be installed in conduit. Any variation to this must be under the direction of ETSA. Spare conduit installation under a carriageway is to be as per section 5.2. and 5.4 of this standard. For a primary cable network that is buried direct in the primary trench in a road reserve such as a single customer network extension and a common service trench for

Cables

50mm

Cable circuit separation 50mm minimum (refer 4.1)

25mm

25mm

Bottom of trench

Conduit

Bedding Sand



a development there is a requirement for spare conduits. Spare conduits installed at a road crossing will need to match the spare conduits in the primary trench. The road crossing conduits need to be continuous with the primary trench spare conduits. These conduits will be in addition to the conduits at a road crossing that will be utilised for a direct buried cable installation. A road crossing for a low voltage tee off (such as a common service trench) that is not part of a continuous run of cable only requires a conduit for a cable. Conduits installed at a road crossing that are for a direct buried cable installation shall extend the full width of the carriageway and extend 900mm into the footpath verge from the back of kerb. The electrical designer and contractor responsible for conduit installation at road crossings should ensure that the appropriate number of conduits are installed. Any road crossing excavation for continuous conduits needs to consider the cover and trench floor invert of the conduits that are to be installed in the road verge. 4.3 Requirements for Transport SA Roads

Transport SA have very specific requirements for any work being undertaken on a Transport SA (TSA) controlled road. The requirements include both excavation and traffic management and apply to overhead and underground works. The Transport SA specification for the Excavation and Reinstatement of Road Pavement is available from TSA on (tel 82268222). ETSA Utilities recommends that any contractor involved with the installation of either underground or overhead electrical works on a TSA road obtain the latest TSA Standard Specification and be fully conversant with all of the requirements. Roadside Significant Sites of an environmental or cultural significance must be considered by both the designer and the contractor. In country regions TSA have highlighted most TSA controlled roadside sites with a distinctive but discreet marker. Information and a list of Roadside Significant sites is available from the Land Development Account Manager at Keswick on 84045439. Some of the relevant sections of the specification dated February 2003 are detailed below. 4.3.1. Open trenching

Most trenching involves work on medium or heavily trafficked roads with an asphalt surface. There is a requirement that all services must be at a minimum depth of 1 metre cover. Any trenching involving an ETSA Utilities installation and other authorities may require a wider trench to ensure that appropriate separations are achieve without shoring requirements. Reinstatement needs to be as per the TSA standard specification. Excavated material can not normally be reused.



4.3.2. Trenchless method

Multiple conduits can be passed through a single bore or tunnel. There is a requirement though for multiple bores to have a minimum spacing of 10D between individual bores. where D = the diameter of the largest conduit. The minimum depth of a trenchless bore is 1.5 metres.

4.3.3. TSA Notification

The designer The electrical designer should submit any design to TSA for comment where any ETSA infrastructure, ie, poles, cable or conduit, will be running parallel to the kerb for some distance. This is to ensure any installation takes into account any future road widening. The Constructor An electrical or civil contractor will need to submit a “Notification of Works Impacting SA Roads“ form NICC-251 (refer to sect 15.0 for access) 5 working days prior to the commencement of works. Any civil works that will be undertaken on a TSA road over a period greater then one day requires 4 weeks notice. The notice is required for the following: • Any work that requires traffic management

This includes work on overhead mains • An open trench and trenchless boring • Any cable pulling through installed conduits.

4.3.4 Traffic Control Notification

The Metropolitan Traffic Control Centre - telephone 1800018313 – must be notified of any ETSA and civil works that require TSA approval (refer 4.3.3). The centre needs notification 15 minutes prior to work commencing and 15 minutes after the road has reopened.

4.3.5. Installation Details

Minimum 1.5 metres

Ground level

10 X 125mm = 1.25m minimum 100mm conduit

125mm conduit

Bore 1 Bore 2



There is a requirement that TSA receives within 3 days of the completion of works a log of any excavation with the construction date, location and depths and details of the reinstatement. ETSA Utilities also requires a copy of the installation details and who undertook the civil works with the “Civil Works Compliance” form. The form is a part the electrical works compliance and connection process.

4.3.6 Emergency Work

TSA requires verbal notification to the appropriate TSA representative at the earliest opportunity. This must be followed with the submission of the “Notification of Works Impacting SA Roads “ form within 24 hours of the emergency.

4.3.6. Maintenance Period

The contractor undertaking the civil component of the electrical works associated with the TSA road crossing will be responsible for the cost of making good any settlement or other deteriation in the reinstated excavation for the maintenance period which is one year.

4.4. Installation of Conduits Within Railway Boundaries Australian Standard AS4799 – 2000 “Installation of underground utility services and pipelines within railway boundaries” covers the requirements for both the design and installation of electrical infrastructure within a railway property. There is specific design information and approvals that are needed for right of entry as well as easement agreements. The form “ Application to Cross Railways With Electric Power Cables” NICC-252 (refer to sect 15.0 for access) must be filled out by the designer a minimum of 28 working days prior to any work taking place and forwarded to;

ETSA Utilities Easements Coordinator level 3, 1 Anzac Highway Keswick 5035 Telephone 84045897 fax 84045193

You will need to supply a preliminary design drawing or a section of DCDB with street names, rail lines and the crossing point marked. There are a number of authorities that ETSA may require approval from.

• Australian Rail and Track Corporation • Trans Adelaide • Australian Southern railroad • Transport SA

Confirmation that any conduit to be installed satisfies the design load for the railway loading may be required. Confirmation from the railway authority that the electrical design has approval will be required prior to ETSA Utilities issuing a Specification Compliance.



An electrical conduit should be a minimum of 2metres deep under any rail line and for a 3metre distance beyond the outer rails. Conduits in other locations in a railway property must have 1 metre minimum cover. A railway authority may approve a lesser depth, but the depth must not be less then the ETSA Utilities standard. 4.5 Clearances between Services.

Comms plant pipe

Comms plant pits

Gas pipes ETSA LV power

ETSA HV power

Comms plant pipe

150 150 200 100 300

Comms plant pits

150 1000 200 100 100

Gas pipes 200 200 X 200 200 ETSA LV

power 100 100 200 X X

ETSA HV power

300 100 200 X X

X = undefined in this application. All clearances are in millimetres Comms = Telecommunications Note: These clearances are applicable for the full circumference of the service (360°) These are minimum separations. For any other authority a minimum separation of 150mm is required. Greater separation may be requested in the ETSA specification from time to time. To achieve these clearances it may be necessary to increase the cover on ETSA cables and/or conduit or increase the trench width. 4.6 Changes in levels and directional changes The depth of any conduit installation in the carriageway should match that of any conduit installation on the road verge (footpath). If this is not achievable the cover at the end of a conduit at a road crossing should be at the same level as the conduit in the verge. Conduit bends may need to be installed to achieve this. Straight lengths of the standard 80 and 100mm very light duty / class 4.5 conduit can be subjected to a minor degree of bending (approximately 10 - 15 degrees over the length of the conduit) Any deviation greater then 15 degrees will require the installation of appropriate bends.

Conduit is not to be installed with a kink in its length under any circumstances. Any section that is damaged will need to be repaired prior to ETSA accepting the asset. Any major variation to the depth of a conduit will have an impact on the ease the electrical installer will have installing a cable in a conduit. A gradient rise or fall should be limited to 100mm per metre for the primary run of ETSA cables and



conduits. Appropriate bends with the smallest radius requirement to achieve a satisfactory clearance to other of services should be utilised. Retrospective undergrounding projects will provide challenges to the civil contractor from time to time when other service providers infrastructure is encountered within the trench. It will be the civil contractors responsibility to resolve these issues and the assistance of the Project Officer should be sought to ensure that a resolution is agreed on that is to the satisfaction of ETSA Utilities prior to construction. Below are some examples of conflict and possible solutions

Preferredgradient rise/fall

of conduit100mm per

1metre

ETSAconduit

NoteIf Y > 1.5m it may bepreferreble to goover service.

150mmminimum under service.

G.L.

X Sharp bends

X Couplinglocation is notappropriate if there isany tension. Thiscreates a lip whichcan damage cables

`Y’

INCORRECT PREFERRED

G.L.

AlternativeConduitroute

The example shows an in-appropriate conduit coupling with tension applies to both a straight length of conduit and a bend. It is important that the developer and electrical contractor establish appropriate ground levels at the time of the installation of the electrical works to ensure that there is no requirement to alter ground levels by a third party after installation. Under the Electricity Corporations Act 1999 the SA Independent Regulator can impose a fine for any breach.

Part 6 of this Act states the following:

38. (1) A person must not, without the written authority of the electricity infrastructure operator –

cut away, excavate or remove, or cause to be cut away excavated or removed, earth or material supporting electricity infrastructure so as to endanger the stability of the infrastructure.

4.7 Common Service Trench A Common Service Trench is normally installed as part of a greenfield housing project. The trench is the responsibility of the Developer and contains electrical and other infrastructure providers.



A trench will normally be 600 mm wide but could be up to 1200 mm wide depending on soil type and footpath location. With consultation with the electrical contractor, a width of 450 mm may be acceptable. The design drawings should specify any non-typical width.

Reference should be made to the “Services in Streets Code” for any trench location in a road reserve.

The depth of the trench shall be such as to achieve a minimum cover of 750 mm above conduits and 1000 mm above all direct buried cables to finished ground level. A typical cross section of trench occupied by the underground mains, Telstra and Gas is shown below

:

Typical width

(Refer to Servicesin Streets Code)

50mm

GAS

TELSTRA

750 mm

450mm

600mm

FOOTPATH

BEDDINGSAND

Property line

1600mm 600 mm

COMMON SERVICE TRENCHmain Side

KERB

LV HV P/L

50mm

1000 mm

Spare conduit

Cables buried direct

Top ofbedding sand

Notes

Refer section 4.1

50mm

Typical width

50mm

GAS

TELSTRA 750 mmminm at thefinishedroad servicelevel at thekerb invertFor a TSAroad refer tosect 4.3

450mm

600mm

BEDDING SAND

600 mm

COMMON SERVICE TRENCH - Road Crossing (non TSA road)

NoteCover slabs or warning tape isto be placed 75 mm aboveETSA plant if ETSA is theonly occupant of the roadcrossing

SPARE CONDUIT

NotesRefer section4.1

LV HV P/L

road level

4.8. Trenching for Retrospective Undergrounding (eg PLEC schemes)

Trench dimensions shall be sufficient to satisfy the minimum dimensions and clearances ETSA specifies in this Standard or as specified in the ETSA specification. The designer will need to also consider for each installation the available space and proximity to other services.

The preferred method of trenching in an existing road reserve which is located in a busy footpath and vehicular traffic area is to install a fully conduited system at the appropriate depth and back fill on completion of specific sections. A draw wire



should be installed for any future cable installations. This method of installation minimises disruption to footpath and vehicular traffic and business premises.

450 mm

Additional conduitRefer 5.2

50mm

Gas, when applicable

Telstra, when applicable

750mm

600mm

Kerb

LV HV P/L 50mm

Warningtape

200mmmaxm

Property line Footpath

RETROSPECTIVE UNDERGROUNDING (PLEC)COMMON SERVICE TRENCH

Bedding sand NotesRefer tosection4.1

Additional conduitRefer to 5.2.

50mm

750 mm

Bedding sand

Kerb

LV HV P/L 50mm

Warning tape

Property line Footpath

RETROSPECTIVE UNDERGROUNDING (PLEC)ETSA ONLY TRENCH

200mmmaxm

Notes

Refersection 4.1

4.8.1 Pit Installations

There are a number of pits of increasing size that are available and the pit that is to be installed needs to be appropriate for the purpose. The designer also needs to be mind-full of other services.

When conduits are installed into the body of a pit, the conduit needs to be 25 – 50mm inside the body. All conduit edges are to have no sharp edges. All conduit entries are to be capped by the contractor to stop the entry of foreign material between the time of the conduit installation and the installation of ETSA cables. Refer to section 5.10.

Expanding foam or silicon should be utilised as a sealer at the conduit entry point into the wall of a service pillar if the conduit is not a tight fit.



Note1 Refer to E1921 sht 2.1

for standard arrangements2 Refer to E1921 sht 6.1 to 6.4

for assembly details3 A P5 pit is preferred for LV

cable junctions and servicearrangements for approvedbelow ground connections

Conduit to finish25mm - 50mm inside pit

CABLE & CONDUIT ENTRY INTO JUNCTION PITS

Extended P5 pit(1 Standard body plus oneshortened body or collar)at preferred 985mm invert

Preferred 0 – 40mm to pitbottom for low voltagecable entry to ensureappropriate room forcable cones

5.0 CONDUIT REQUIREMENTS

5.1 General

Cables shall be installed in conduits in the following circumstances:

• Road crossings

• Full length of pathways with restricted access ie, a pathway between fenced allotments)

• Cables installed through easements. • Public lighting cables • Retrospective undergrounding (i.e. PLEC Projects) • On private property where cables vest in ETSA Utilities (Refer to section

6.0 for all options) Earth cables do not need to be installed in conduits Where there will be access roads, driveways and footpath crossings greater then 2.5 metres in width, conduits for a cable installation as well as spare conduit requirements may need to be included in a design. Full details of the conduits must be included on a design drawing and the “As Constructed” drawing must reflect the actual installation. Any breaks in a continuous conduit installation must be noted as must any changes in the as installed conduit size.

11kV cables must not be installed in the same conduit as low voltage cables

5.2 Spare conduit provision

Spare conduits are required to be included in the design and installed for the following;

5.2.1 Wherever an electrical cable is buried direct, ie in a road reserve. The conduit installation needs to be such that any buried direct cable can be reinstated in a spare conduit. As an example; There are three circuits of low voltage and one circuit of 300mm2 high voltage cable being buried direct in a common service trench. In accordance with section 5.4 ‘Conduit Sizes’ the cables require the following; For the Low voltage: 3 x 80mm VLD conduit



For the high voltage: 3x 80mm VLD conduit Note: Where one LV circuit consists of two or more parallel bundles of cables, a spare conduit must be provided for each bundle of cables.

5.2.2 When a cable is installed in a conduit

To ensure future access to ETSA infrastructure is kept to a minimum there is a requirement where cables are to be installed in conduit for additional conduits. Unless specified differently in the ETSA specification the requirement is: A PLEC project – One spare conduit for all of the low voltage circuits

One spare conduit for all of the high voltage circuits up to and including 300mm2. One spare conduit per phase for any 630mm2 high voltage installation

A Customer project ( ie, through any easement) For every 3 conduits (or part there of) installed that are to be occupied by cables, there is one additional conduit included in the installation.

As an example,

There are 3 cable circuits installed in conduits made up of 2 low voltage circuits in 2 x 80mm (or 100mm) conduits and one 300mm2 high voltage cable with one phase installed in a each of 3 x 80mm conduits.

Note: Any public lighting cable installed in a medium or heavy duty conduit is excluded from the requirements of 5.2.2

There are a total of 5 conduits with cables. With a requirement of one spare conduit per 3 occupied conduits, or part thereof, there will need to be 2 additional conduits included in the installation.

5.2.3. Road crossings

There is a requirement for spare conduits as well as the conduits that are to be utilised at the time of the cable installation at road crossings. Refer to section 4.2 of this standard for details.

5.3 Spare Conduit and Bend Requirements

Where spare conduits are required (refer to section 5.0), the extent of the installation should satisfy the following table: Situation Requirement Common trench T intersections no bend requirement Transformer vaults - general no bend requirement Transformer vault for a future stage bends required Trench direction changes greater than 90 deg no bend requirement Trench direction changes less than 90 deg Bends required Road crossing - primary cable run Continuous Road crossing – tee off/non continuous nil



The requirement for bends will need to be assessed at the time of installation as well as at the time of trench design layout.

5.4 Conduit Sizes

While the chart specifies minimum conduit sizes, a larger conduit may be installed on the proviso that the conduit can be made continuous with any existing or future continuous conduit installation. A conduit of a higher classification can be utilised then those specified.

The minimum size of a conduit for a specific cable size are as follows: Cable Circuit Conduit Size Conduit Bend LV Main & Service bundled

1 x 80mm VLD 1800 radius, Light duty

HV 35mm2 1 x 80mm VLD 1800 radius, Light duty HV 95mm2 1 x 100mm VLD 1800 radius, Light duty HV 300mm2 and 630mm2

3 x 80mm VLD 1800 radius, Light duty

Public Lighting 1 x 32mm HD 312 radius, Heavy duty CBD installation No x 125mm VLD

The ETSA standard class 4.5 is equivalent to very light duty (VLD) The ETSA standard class 6.0 is equivalent to light duty (LD)

Care must be taken in joining conduits. Different grades have different internal diameters and the resultant raised internal edge has the potential to damage the outer layer of cable during cable pulling. 5.5 Compliance to Australian Standard Conduits and couplings shall be uPVC material and meet the requirements of AS/NZS 2053 Parts 1 and 2 for Rigid Plain designation. The conduit will be marked with the word ‘electrical’, the conduit size and class, eg ‘ELECTRICAL DUCTING 100 mm 4.5 class’. No other form of rigid conduit is permitted without the approval of the Network Standards Manager . Conduits shall also meet the requirements of AS/NZS 1477 - 1996 for the Test for Impact at 20 degrees C. 5.6 Colour of Conduit

Conduits and couplings shall be light orange in colour. 5.7 Conduit for Directional Boring

The conduit used for directional boring must : a) meet our minimum requirements and AS/NZS4130. b) be able to withstand the forces involved in the directional boring process.



c) be light orange in colour. Black conduit with orange stripes may be utilised with the approval of the project officer if orange conduit is not available.

d) be of size and characteristics to allow the cable to achieve its current rating. e) Be anchored at conduit entry/exit appropriately to maintain it’s horizontal

profile. The polyethelyne material has a ’memory’ and will attempt to coil up. This will introduce stress at conduit transition locations and at the start/end of a directional boring conduit installation.

5.8 Design of Conduit Installation Conduit designs shall be prepared to ensure that pulling tensions do not exceed the maximum permissible as required by the Construction Standard TS 087. Installation details and techniques for cable pulling through conduits are in E1906. Reference to an indication of cable pulling tensions is listed in E1910 sheet 4.2 5.9 Conduit Installation Conduits shall be laid on an evenly bedded 50mm thick layer of well-graded sand substantially free from lumps and particles having a dimension in excess of 6mm. After the laying of each length, bedding material shall be placed and tamped to hold the conduit securely in position and provide a cover of 50mm when compacted. A minimum of one hour should be allowed between any conduit gluing and the installation a draw rope. The gluing of conduits should be carried out to the manufacturer’s recommendations.

Draw rope with a 6mm minimum diameter and made from a material approved by ETSA Utilities may be required for some projects. The exposed ends of all conduits shall be cleanly and squarely cut and fitted with PVC caps to prevent the entry of water, dirt or other foreign matter.

Floor of trench /opening for bore

Edge of entry/exit hole

Securing the end of directional boring conduit

Directional boring conduit

End of polyethylene pipe to be concrete encased or sandbagged



For spare conduits in a group, the position of the ends shall not vary by more than 300mm. Where conduits are installed in layers, the ends shall be positioned horizontally. Conduits between new and existing subdivisions must be joined together. Cable markers are required wherever ETSA conduits/ cables pass through private property. Refer to E1979 for installation details.

5.10 Sealing of Conduits For a cable Installation Where cables have been installed in conduits, a conduit end shall be adequately sealed to prevent the entrance of dirt, stones, white ants and moisture into the conduit by the use of polyethylene expanded foam applied in accordance with the manufacturer's instructions. The expanding foam should not encroach into the conduit any further then 75mm. This will ensure that the foam/cable can be easily removed if the need arises.

Sealing of conduits with cables

For conduits with no cables The use of end caps is a requirement for any conduit that is to remain vacant. This includes the installation of end caps on a temporary basis on a conduit that will not have a cable installed immediately.

Description Stock Item No Cap, push on 40mm for consumers conduit Cap, push on 50mm for consumers conduit NC 6462 Cap, push on 80mm NC 6470 Cap, push on 100mm NC 6501

6.0 TRENCHING ON PRIVATE PROPERTY

Trench dimensions shall be sufficient to satisfy the minimum ETSA requirements as specified in this Technical Standard and an ETSA specification.

There are three options for cable installation: Diagram A. Install all cables in conduits buried at a depth of 1000 mm as shown. The polymeric cover slabs are not required but may be installed if desired. Diagram B Install cables in conduit at a depth of 750mm. Install polymeric cover slabs (if required) and warning tape as shown. Conduit requirements are as per section 5.0.

Scrunched plastic or newspaper

Cable

Approx 75mm Expanding foam



Diagram C Install cables buried direct at a depth of 1000 mm. Spare conduits as section 5 are required for the cable circuits that are to be installed. Polymeric cover slabs are still to be installed.

• Warning tape is required in all cases.

The general trench configuration shall be in accordance with the following diagrams.

50mm

BEDDINGSAND

PL LV Spare HV

200 mmmaxm

WARNINGTAPE

50mm

1000mm

50mm

750 mmminm.

BEDDINGSAND

P/L LV Spare HV

POLYMERICCOVER SLAB

50mm

75mmmaxm

Diagram A cable in conduit at 1000 mm Diagram B Cable in conduit at 750mm

750 mmminm

1000 mm

50mmBEDDINGSAND

P/L LV HV

POLYMERICCOVER SLAB

5mm thick

50mm

Spare conduits

75mmmaxm

Diagram C

Cable buried direct

7.0 TRENCHING FOR SINGLE CUSTOMER ON VERGE (Option)

Trench dimensions shall be determined as required by ETSA Utilities and the customer, and will depend on the available space and proximity to other services.

Where the cables are to be direct buried, the trench configuration shall be in accordance with the following diagram.

Notes Refer section 4.1



• •

Spare conduit

Cables buried directPublic lighting can bein conduit or burieddirect

50mm

1000 mmBEDDING

SAND

50mm

750mmNotesRefer section 4.1

ROAD VERGE -SINGLE CUSTOMER

Any ETSA cable system that needs to be located under a road needs to satisfy either the requirements detailed in section 4.5. for common service trenches or section 4.3 if it is a Transport SA road

In situations where public lighting circuits within conduits are to be located in a trench alone, (eg no adjacent power circuits or spare conduits), the minimum cover shall be 600mm with warning tape installed at 400 mm. Any public lighting network that is a Customer Lantern Energy Rate (CLER) or is fed from a metered supply point requires a minimum separation of 150mm from any ETSA infrastructure.

8.0 EXCAVATION FOR VAULTS The excavation for vaults shall be as follows:

(a) Padmount Transformer Vaults:

the dimensions are in the order of 1850 long x 1000 wide x 1250 deep, totalling approximately 2.5 m³ of spoil to be excavated.

(b) Switching Cubicle Vaults:

the dimensions are in the order of 2250 long x 1000 wide x 1175 deep, totalling approximately 2.7 m³ of spoil to be excavated.

The spoil requiring excavation for the above two cases allows working room for

the placement of cables in conjunction with installation of the vaults. 9.0. BEDDING SAND Bedding sand must be : a) used prior to and after the laying of cables. b) layed below and above the cable and conduits to the depths shown in section 3 of this

standard c) used under any cable vault and service pit installation. d) lightly and evenly compacted by tamping with feet or by rolling the trench bed prior to

backfilling. Minimum coverage requirements must be maintained. e) in compliance with the ETSA specification:



Some common sand types are designated as DS4B and PM64. The specification for these types differs from the ETSA standard. It is the contractors responsibility to ensure the installed sand meets the ETSA specification.

TEST METHOD TEST

PERMITTED TEST VALUES

Grading Percent Passing

AS1141.11 Sieve Sizes mm

AS1152 4.75 100 2.36 98 - 100 1.18 94 - 100 0.6 85 - 100 0.425 55 - 100 0.3 25 - 100 0.15 5 - 40 0.075 0 - 10 AS1289 C3.1 Plasticity Index Maximum 6

(non plastic)

10.0 POLYMERIC CABLE COVERS / MARKER TAPE

The stock item for the 5mm polymeric cable cover is RN 0202 which is supplied as a 15 metre long roll, 300mm wide. To satisfy AS/NZS 3000 the strip must be placed no more than 75mm above ETSA infrastructure and must overlap the ETSA infrastructure by 40mm per side. Marker tape is a requirement for PLEC projects. For any other installation, if the conduits installed for electrical infrastructure are not a light orange in colour, marker tape will be required to be installed not more then 200mm above the conduits. If polymeric cable covers have been installed marker tape is not a requirement

11.0 BACKFILLING and CONSOLIDATION The backfilling of trenches and excavations will be carried out as soon as practicable

after cable and conduit laying is completed. Before backfilling operations of any trench excavation commence, surplus jointing

materials, any waste materials and all rubbish including timber and foreign material will be removed from the trench.

Backfill material will not be placed in any excavation containing free water or slurry.



Backfilling material must be clean and completely free from all fibrous and vegetable matter and other material which may attract or be attacked by termites.

Excavated material from the trench may be used as backfill above the bedding sand provided that this material is predominantly soil. If the material does contain any metal or rocks, then it may only be used if : • the amount of metal and rocks is less than 20% of the material (by volume) • the metal and rocks pass through a 50 mm screen. Where conduits are laid beneath other buried services, the backfill beneath such services is adequately compacted such that :

(a) no voids between conduit layers, and (b) the other buried service(s) is adequately supported to prevent damage.

Consolidation of the backfilled excavations will be in accordance with the local

Council or Transport SA specifications as appropriate. 12.0 CIVIL WORKS

12.1 Applicant’s Responsibilities The Applicant or an agent of the applicant shall be responsible for:

• Ensuring that all allotment pegs, including any replacement pegs, easement pegs and level pegs are correctly placed, clearly visible, and numbered to show allotment numbers, reserves, easements etc.

• Carrying out and co-ordinating all the pegging, trenching, backfilling,

reinstatement, levelling, and associated work including retaining walls, necessary for the installation of cables, transformers and switching stations, service pits and pillars and lighting columns.

• The safety of the open trench and any liability arising from the Applicant's

works. This includes ensuring that there is suitable clearance between any excavation and existing ETSA infrastructure, including poles and footings. A financial penalty can be applied by the industry Regulator for any unlawfull interference

• All street and ground openings and all costs including the compaction and

reinstatement of road and footpath surfaces and services where disturbed or damaged, to the satisfaction of the authority or owner concerned.

• Arrangements with the local authorities and public service utilities for the

temporary disturbance of any driveway, culvert, pipe, drain, kerb, survey mark etc.

• Excavations of padmount transformer vaults and footings and switching

cubicle vaults and footings and the reinstatement of the remaining excavation surrounding vaults.



• Damage caused to vaults and associated equipment during backfilling and compaction

13.0 CONTAMINATED SOIL

Where ETSA Utilities constructs the Works, it is the Applicant's responsibility to ensure that the soil is free from any contaminants that may be a risk to the health of ETSA Utilities’ distribution workers. Written assurance may be required to demonstrate that the soil is free from contamination and if necessary a report detailing known contamination and steps taken to alleviate the health risks. Further testing may be required before ETSA Utilities agrees to work on the site.

14.0 CIVIL WORKS COMPLIANCE Part of ETSA Utilities regulatory requirements includes an undertaking that any electrical installation is compliant. Civil works and conduit installation forms a part of the ETSA electrical asset and must be at a standard that satisfies all of the relevant ETSA Utilities standards and specifications. To assist in the verification that the civil works are to standard a “Civil Work Compliance” form is required from the civil contractor as part of the electrical compliance. There is a spreadsheet that details responsibilities for both the “Civil Works Notification” form and the “Civil Works Compliance” form in appendix A of this specification. 14.1 Civil Works Notification Civil works form a component of the asset inspection and vesting process. The Civil Works Notification form NICC-453 (refer to sect 15.0 for access to the form) must be submitted to the appropriate ETSA Utilities representative. The following notice is required:

A section (contestable projects) 10 working days notice B section 5 working days notice

14.2 Civil Works Compliance The “Civil Works Compliance” form NICC-452 (refer to sect 15.0 for access to the form) must be completed by the civil contractor and forwarded on to the Electrical Contractor or the nominated ETSA Utilities Officer. The form is an integral component of the “Certificate of ETSA Utilities Electrical Compliance” If it is not available at the time of the final asset audit and sign off there is the possibility that the customer’s connection will be delayed.

15.0 FURTHER INFORMATION

A comprehensive listing of information bulletins and forms that are of interest to a customer and a contractor can be found on the ETSA Utilities web page



www.etsautilities.com.au for external users. Open services/business services/ Network Information Any ETSA Utilities employee has access via the Intranet index and opening up Network/Quality Management Systems/Network Information. Some of the information that is relevant to this technical standard include the following; • “Civil Contractors Utilised by ETSA Utilities” - NICC-203 • For a TSA road: “The Notification of Works Impacting SA Roads” - NICC-251 • For a railway line: “ Application to Cross Railways With Electric Power Cables”

NICC-252 • “Civil Works Notification” form NICC-453 • “Civil Works Compliance” form NICC-452 • “Terms & Conditions for Network Installation by a Contractor”

Trenching & Conduit Standard Technical Standard TS - 085

Issued: April 05 TS -085 Authorised: J Ali 11/04/05 Appendix A

CIVIL WORKS NOTIFICATION & COMPLIANCE RESPONSIBILITY

CaMS / BSO (minor works only)

CaMS / Contract S’visor (minor & major project)

CPO (major projects only)

Customer (when responsible for trenching)

Civil Contractor

Civil Works notification form NICC - 453 Intranet: Network/QMS/Network Information

Customer doing the trenching

1. Fill in B: Contract Supervisor / TSW8 2. Issue to customer

1. Insert point of contact: Compliance Co-ord 2. Issue to customer as part of information pack

Customer to forward form to the contracted civil contractor

Return form to: A for a contestable project B for all other projects (Contract Supervisor / TSW8)

ETSA doing the trenching

1. Fill in B: Contract Supervisor / TSW8

2. Issue to civil contractor

Return form to: Contract Supervisor / TSW8

Civil Works Compliance form NICC - 452 Intranet Network/QMS/Network Information

Customer doing the trenching

1. Insert name of Contract Supervisor / TSW8 2. Issue to customer

1. Highlight point of contact as electrical contractor 2. Issue as part of information pack

1. Customer to insert electrical contractor details

2. Forward form to civil contractor

Return form to: Electrical contractor. If unknown, the customer

ETSA doing the trenching

1. Fill in ETSA Contract Supervsor / TSW8 2. Issue to civil contractor

Return form to: Electrical contractor. If unknown, Contract Supervisor / TSW8

Note: The “Civil Works Compliance” form must be completed for all projects with a trenching component as

it is a prerequisite to acceptance of the “Certificate of ETSA Utilities Electrical Compliance”

Documents

TRENCHING AND CONDUIT STANDARD FOR …tkne.net/downloads/power/cabels3/Trenching for underground cables.pdf · This Technical Standard is based on the Electricity (General) Regulations