Please find below frequently asked questions about Earlwood to Summer Hill cable project. The community feedback summary, which can viewed via the link at top right of the project page, has further questions (and answers) from the community information sessions.
1. How does Ausgrid avoid existing pipes and underground infrastructure?
Ausgrid has already completed desktop studies, using Dial Before You Dig drawings that identify existing services. In addition, site investigations are completed to physically identify underground services as well assess the ground conditions. In areas where they are many underground services, Ausgrid would modify construction activities, often hand digging around the infrastructure.
2. What depth are the cables?
Generally, trenches are dug using an excavator and are approximately 1.5 metres deep and 1.3 metres wide with plastic conduits (pipes) being placed in the trench.
3. Do you put these cables in a trench with other services?
Ausgrid doesn’t generally put cables in trenches with other services other than fibre optic cables for our network, as there are technical requirements that require certain distances to be kept from other services. There are also safety considerations when working near cables that are in operation. However where possible and it is efficient to do so, like for this project, Ausgrid will place a spare conduit in the trench to be utilised later, if required, without having to trench the road again.
4. If you trench in Waterside Crescent, how will it affect Council’s plans to resurface the area?
Canterbury Bankstown Council has advised Ausgrid about their plans for Waterside Crescent and we have planned to work together to minimise impacts. Ausgrid and Council would work together to coordinate works where possible to try to minimise disruption and impacts on residents on streets where the new cables would be laid.
5. What is the distance between joint bays?
Ausgrid generally installs joint bays every 500 to 570 metres. The exact location of joint bays along the cable routes would be finalised once the cable route is confirmed and a contract awarded. The contractor would then prepare a detailed project design, including the location of all joint bays.
6. Do you put joint bays in driveways?
No, Ausgrid tries to avoid driveways. As soon as the project team has planned where the joint bays will be located, consultation starts with the immediate neighbours. This is done at least 21 days before the joint bay is excavated in the roadway. Ausgrid and the contractor make contact with all residents adjacent to the joint bays well in advance of work starting to discuss the construction process. Generally joint bays remain in place for a couple of months but access to properties is maintained. This amount of time is required to allow the pit to be excavated, the cables to be pulled through and specialist crews to undertake cable joining work inside the bay. This is done in stages.
7. How long is the construction process?
Ausgrid estimates that it would take about one year to finish the construction of the entire project and then an additional six months to test and commission the cables and complete the final restoration of the affected areas. After a contractor has been confirmed and further planning completed, a more detailed program will be prepared. The contractor will be able to advise where they plan to start the works and whether there would be several crews working at multiple locations.
8. Will you put the cables in the grass verge?
Cables of this voltage are generally installed in the roadway with the pavements and grass verge allocated for lower voltage cables or power lines.
9. Will the final road surface be safe for cyclists to use, i.e. no lip between restored areas and existing road?
As already mentioned, trenches are generally located within the centre of the road, however the cable alignment is largely determined by existing services in the roadway. During construction, control measures would be put in place to ensure the safety of cyclists. Steel plates are usually used to cover any open trenches between shifts and these areas would be sign posted. Trenches are temporarily restored with hot mix asphalt which is equivalent to a normal road surface (except with seams down either side of the trench). The temporarily restored areas are then regularly monitored to ensure surfaces are safe for all road traffic. At a later date the affected section of the road is reinstated permanently in consultation with local councils or the relevant road authority by specialist road construction crews.
10. How do you know where the existing cables and other infrastructure in the ground are located?
As already mentioned, Ausgrid completes desktop studies, using Dial Before You Dig drawings that identify existing services. In addition before any work starts, site investigations are completed to physically identify underground services as well assess the ground conditions. In areas where they are many underground services, Ausgrid would modify construction activities often hand digging around the infrastructure.
11. How will Ausgrid work with Council to avoid digging up roads that they plan to resurface?
Ausgrid has met early with councils in the areas where we are planning to install cables to receive local information as well as to get details on their program of works. These meetings continue throughout all stages of the project to keep councils updated on our plans and to coordinate works where possible to try to minimise having to excavate after any council road restoration.
1. Why can’t Ausgrid go back to the existing route?
Ausgrid considered the existing cable route as one of the first options as it is the most direct route between substations. Following community feedback, the project team looked at this option again. There are several factors that make this option less feasible than the other options that were being considered. One is not being able to utilise the Melford Street Bridge as the construction of the bridge, essentially a concrete box, wouldn’t allow for the new cables to be kept sufficiently insulated to be able to work efficiently and meet demand in the future.
The second factor is that the Karool Bridge which currently contains Ausgrid’s existing cables needs to be replaced. Ausgrid has been talking with Canterbury Bankstown Council about their plans to replace the bridge including time frames and costs to see if this could be a viable option.
The other factor is that the existing route runs along Old Canterbury Road. As it is a busy road, it is likely that the relevant road authority would only allow Ausgrid to work at night. This would cause extended disruption to surrounding residents. It is also a concrete road which is much more expensive to excavate and restore than asphalt roads, is also is more expensive and takes more time to complete.
1. What is the total budget?
As part of the planning process, Ausgrid is required to minimise project costs as much as possible (so additional costs aren’t passed onto electricity customers). The project team estimated the cost of the project based on the preferred route. Approval is then sought to fund the project. This process includes having to comprehensively justify the requested funding.
2. What does Ausgrid do with the existing cables?
The existing cables remain in the roadway after they have been safely removed from service. Ausgrid seeks to minimise cost and disruption to the community by not removing the redundant cables.
1. Why can’t you bore under the Cooks River next to the Karool Bridge?
While a bore is feasible, it is not Ausgrid’s preferred option due to; the costs associated with this type of crossing, potential environmental risks, as well as technical considerations (cables not performing as well when installed at depth and at certain ground conditions).
2. What determines the cost of a project?
The cost of a project is determined by factors which include route length, crossings, i.e. bores are generally more expensive, type of road surfaces to be replaced, i.e. concrete is generally more expensive than asphalt, working at night rather than day works – cost of resources.
3. If the length of the route is a driver, why don’t you put in a new bridge in Karool Avenue next to the existing bridge (and cables)?
The length of the route is a driver as the most direct route can often cost less and cause less community disruption by passing less homes, but it is just one of that factors that Ausgrid considers in planning a cable route. The benefits of a more direct route are weighed against the cost of a new bridge, the disruption caused by the construction of a new bridge, and the time it would take to get the necessary approvals and to construct. However as already mentioned, Canterbury Bankstown Council is planning to replace the existing Karool Bridge and Ausgrid has been talking with them about time frames and costs to see if this option is feasible. Another key consideration is the crossing of the Bankstown Line railway. Ausgrid considers the Foord Avenue underpass option to best meet all the factors wea re required to consider during the planning of a cable project.
4. Why can’t you build a power line over the Cooks River?
Ausgrid could potentially construct a new power line over the Cooks River; however Ausgrid feels that the broader community would find this aesthetically unacceptable. As the cables would be underground and then overhead to cross the river, it would also require overhead to underground poles which are also not visually pleasing.
5. What are the costs per metre?
Ausgrid estimates costs per metre from previous similar projects to be able to bench mark and compare route options. As part of the planning process, Ausgrid is then required to minimise project costs as much as possible (to minimise costs being pasted onto electricity customers). Once a preferred route has been proposed, the project team then estimate costs and seek approval for this funding to complete the project. This includes comprehensively justifying the requested funding.
6. What are the costs of the bore?
Like estimating costs per metre, Ausgrid initially estimates bore costs from previous projects to be able to bench mark and compare route options. However it is important to note that the costs are not the only factor when considering major crossings. Other significant factors are environmental and technical risks associated with a bore of this depth and length. Costs are assessed as a cost benefit rather than the cost alone.
7. Why did Ausgrid only choose the two routes from Canterbury to Summer Hill?
Ausgrid initially started with over twelve possible variations on options to install cables between Earlwood and Summer Hill. These were refined after meetings with councils and the local Member of Parliament and further planning. The options presented to the community are the options that Ausgrid thought were potentially feasible and were currently being considered. Following community feedback on these options, Ausgrid has revisited several variations, such as the existing route to reassess as potential options and now has a preferred option.
8. Why doesn’t Ausgrid use Cup and Saucer Creek and then go back down the creek?
Ausgrid is limited in the locations where the cables could exit Canterbury substation due to the number of existing cables there already. In addition, if Ausgrid utilised a crossing of the creek at this location, the entry and exit points would still need to be resolved as it seems that crossing Melford Street or Church Street rail bridges are not feasible. We would also have to consider easements and the likely issue of a lack of space to install new cables in Woolcott Street.
9. Will these new cables replace the overhead power lines that are in the Pat O’Connor reserve area?
No. Ausgrid is replacing existing 33,000 Volt cables that run underground between Earlwood and Summer Hill that are ready to be retired.
10. Will any of the cable route options go through private property?
No, Ausgrid avoids going through private land wherever possible due to the difficulty and time it takes to get an easement and because of the potential community disruption. If Ausgrid were to utilise part of the existing route, an easement would be required through private property.
11. Wouldn’t there be less impacts on the community and environment if Ausgrid used a bore the cross the Cooks River?
Due to the technical difficulty of this type of bore (the bore would have to be deep and long to cross the Cooks River), there is a greater possibility for issues and so it would potentially take longer to complete the work than it would installing cables over an existing bridge. There are also potential environmental risks and technical issues to consider due to the increased depth of cover. Ausgrid generally considers a bridge crossing to have less impact on the community and environment than a bore of this type.
1. Will Ausgrid coordinate works with Council?
It was mentioned by several residents in the Canterbury Bankstown Council local government area that Ausgrid should coordinate works with council’s plans. Ausgrid agrees that the benefits of working with councils means that overall impacts on residents can be minimised. Ausgrid has started planning with Canterbury Bankstown Council on how best to work together to minimise impacts on the community. In Waterside Crescent and at the Ford Avenue underpass, Ausgrid and Council plan to coordinate the timing of respective works.
Where possible, Ausgrid is planning to time works so that the final reinstatement of affected sections would be completed after all works have finished.
1. What will the magnetic fields be from the cables that are planned to be installed in the Foord Avenue bridge?
Modelling of the magnetic fields from the proposed new cables in the Foord Avenue bridge has found that generally that would no change to the existing magnetic field environment under normal conditions.
2. Can the Foord Avenue bridge support the proposed cables?
In regards to the structural integrity of the bridge, Ausgrid’s structural engineers have completed an early assessment and identified that the bridge could support the cables and only minor works would be required.
3. What is the life expectancy of the bridge?
It has been assessed that the life expectancy of the bridge’s components range from 30 to almost 70 years.
4. If the cables are installed on the bridge, does that mean that Council would not be able to replace the bridge in the future?
If the cables were to be installed on the bridge, Ausgrid would likely enter into a type of license agreement with Council but this would not prevent the bridge from having to be replaced if required.
5. Will there be any significant changes to the bridge’s structure (if so, could you supply an artist’s impression)?
Ausgrid is designing the cables to be installed as unobtrusively as possible, i.e. under or on the side of the bridge. The design process has started now there is a preferred cable route. Ausgrid would consider preparing an artist impression only if the design were to significantly alter the appearance of the bridge which we do not plan to do.
6. If you put the cables in the bridge, who would maintain it?
As mentioned above, Council and Ausgrid would likely enter into an agreement that outlines this but generally Council would continue to maintain the bridge and Ausgrid would maintain the cables.
7. The Foord Avenue bridge is a popular bridge used to go to the local school, park and train station. How does Ausgrid plan to complete work on the bridge to minimise impacts on bridge users?
Ausgrid will work to minimise impacts while installing conduits across the bridge (the cables would be pulled through the conduits at a later date on either side of the bridge). Ausgrid would look to work at times when the bridge is used least and will try to minimise any closures. We will complete further consultation about the bridge use as part of our project planning.
8. How long would it take to install the cables across the Foord Avenue Bridge and would access be restricted?
ime frames would depend on the methodology, however as the bridge has been highlighted as a popular way for community to get to the park, to the train station and to schools, Ausgrid would work to minimise impacts from any work as outlined above.
9. What will the magnetic fields be from the cables that are planned to be installed in the Foord Avenue path?
Modelling of the magnetic fields from the new cables has found that generally under normal conditions, there would be no change to the existing magnetic fields.
10. How does Ausgrid plan to complete work in the lane way?
As with Waterside Crescent, Ausgrid plans to coordinate the proposed activities in the path to the bridge with Council.
11. How would the work be completed in the Foord Avenue lane way as it is very narrow?
Ausgrid plans to excavated in the path that runs to the Foord Avenue footbridge on the Earlwood side by using smaller low impact equipment.
1. What is EMF?
Electrical energy involves ‘voltage’, which is the pressure behind the flow of electricity that produces an electric field, and ‘current’ is the quantity of electricity flowing that produces a magnetic field. Electric fields are naturally occurring and can be present in any appliance plugged into a power point and switched ‘on’ (however as electric fields are readily shielded they were not modelled for this proposal). Magnetic fields are only present when electric current is flowing. The strength of a magnetic field depends on the size of the current. Like electric fields, the strength of magnetic fields drops off quickly as you move away from the source.
2. What will the magnetic fields be in my street?
Ausgrid models the magnetic fields that would be found around the proposed cables once they are in service. Modelling is generally prepared using time weighted averages of the electrical load under future loading conditions. The magnetic fields are calculated using time weighted averages on the cables once they are in operation. The modelled magnetic fields are what the Australian Government agency ARPANSA identifies as typical background levels (01.- 2mG).
Magnetic field modelling assists Ausgrid with route planning, in providing information to the community, and as part of preparing the project’s environmental assessment. Independent modelling by consultant Magshield shows that the magnetic fields from the proposed new underground 33,000 volt cables for this project would cause no change to the existing magnetic fields both standing over the proposed cables (measured at 1 metre height) and at properties along streets along the proposed route. The magnetic fields from the joint bays would be higher but would drop down to everyday levels and property boundaries along the route.
3. Where can I get more information on EMF?
Ausgrid can provide more information on magnetic fields generally and in relation to this project. We can also organise visits to take measurements of existing magnetic fields in and around homes. Ausgrid has found on similar projects that this can provide some context to the magnetic fields from the proposed cables in relation to the existing environment. Further information can also be found at Australian Government agency
ARPANSA, the Energy Networks Association (ENA) and the World Health Organization (WHO).
4. Will the levels of electric and magnetic fields (EMF) from the proposed cables be safe and comply with relevant Australian health guidelines?
Safety is Ausgrid’s highest priority. The proposal has been planned on the basis that the new cables can be operated safely in the community and this is Ausgrid’s first and most important consideration. The new cables would operate well within Australian and international health guidelines, with very little, if any change to existing magnetic fields in nearby properties.
5. What is Ausgrid’s approach to EMF?
While there remains a lack of scientific consensus about whether electric and magnetic fields (EMF) can cause any adverse health effects, Ausgrid understands that there is concern in the community about EMF. We take seriously our responsibility to help address these concerns by providing balanced and accurate information about EMF, by taking reasonable steps to limit exposure and by operating all our electrical installations prudently within Australian health guidelines. We also regularly monitor research and policy into EMF and health.
As there is a lot of research and studies regarding health and EMF, Ausgrid is guided by Australian Government agency ARPANSA, which takes a whole of science approach in relation to electricity and health. This includes implementing prudent avoidance measures where practical and feasible, as we will do for this project. Ausgrid's position includes complying with all relevant national and international guidelines.
6. What is the difference between EMF and *mG on your documentation?
Electric and magnetic fields (EMF) are part of the natural environment and are present in the earth’s core and the atmosphere. These fields are also produced wherever electricity or electrical equipment is used. Magnetic fields are only present when electric ‘current’ is flowing. The strength of a magnetic field depends on the size of the current. Like electric fields, the strength of magnetic fields drops off quickly as you move away from the source. While electric fields can be shielded, magnetic fields pass through most materials. As electric fields are naturally shielded, the electricity network generally contributes very little to the electrical fields measured inside a home or office building. For this reason most discussion on EMF usually focuses on magnetic fields. A milliGauss (mG) is the unit of measurement for magnetic fields. When we are talking about EMF in this context, we are generally talking about magnetic fields and the mG is the measurement of these fields.
7. Do magnetic fields accumulate?
Adding magnetic fields from two sources is not a straight forward matter of adding the field strengths. Magnetic fields are vectors and have direction and size. Usually, if two fields come from different sources, the orientation is random and will vary over time. If there are two magnetic fields with random orientation, one field has to be only slightly larger than the other to dominate the average result. For example, if one field is half the size of the other field, it makes only a 10% difference to the total. Therefore, in practice, if we want to know what the field is at a given place, we need usually assess the field from the biggest single source only.
8. What is the acceptable range for magnetic fields?
In the absence of a current Australian standard, Ausgrid follows the current international (ICNIRP) guideline level of 2000mG. It is important to recognise that the numerical limits are based on established health effects. ICNIRP’s fact sheet on the guidelines notes that: “It is the view of ICNIRP that the currently existing scientific evidence that prolonged exposure to low frequency magnetic fields is causally related with an increased risk of childhood leukaemia is too weak to form the basis for exposure guidelines. Thus, the perception of surface electric charge, the direct stimulation of nerve and muscle tissue and the induction of retinal phosphenes are the only well established adverse effects and serve as the basis for guidance.”
9. Should I be concerned about magnetic fields from high voltage cables and links to childhood leukaemia?
Ausgrid’s position on EMF has been adopted in the light of authoritative reviews having concluded that no adverse health effects from exposure to EMF have been established, but recognising that there is, within the community, some genuine public concern about the issue which must be addressed. A further consideration is also the low levels of magnetic fields modelled for the new cables, which are well within the range normally encountered in everyday life at properties along the cable routes.
10. How high would the magnetic fields be on the Foord Avenue footbridge compared to the existing overhead power lines?
Modelling from the magnetic fields from the proposed new cables under the bridge indicate levels are well within international and Australian guidelines.
11. What would the magnetic fields be from the cables if they were installed in this lane way as it is very narrow?
Independent modelling has found that that the magnetic fields from the proposed new cables would be consistent with the existing environment at all properties.
12. What would the magnetic fields be from the joint bays?
While magnetic fields are typically higher at joint bays than in other sections, it is still expected that given the setback from the joint bay to property boundaries, the magnetic fields from the proposed new cables would be consistent with the existing environment.
1. What role does the environmental assessment have in shaping the project options and the route the cables will take?
A Review of Environmental Factors (REF) is currently being drafted on the preferred cable route option. The REF investigates the potential environmental impacts associated with the construction, operation and maintenance of the proposal. It identifies key issues raised during the planning stages and outlines the mitigation measures which have been identified to address any impacts and to minimise any issues. The REF also includes specialist assessments. The REF needs to determine that the project would have minimal effect on the environment for the project to be approved for construction.
2.If there are adverse environmental impacts found when the preferred route has been assessed, does Ausgrid then look at other options?
If adverse environmental impacts are found as a result of this assessment, the project would not proceed until it could be assessed as being not likely to significantly affect the environment. This could include looking at other options.
1. If the new cables are installed across Foord Avenue footbridge, will it affect the adjacent area that has recently been regenerated at the Cooks River bank?
Ausgrid has met with the local ecological volunteer group, the Mud Crabs, on site to discuss potential proposed works in relation to the work they have been doing in the area. While there are no plans to affect this area, Ausgrid would look to work with the Mud Crabs to ensure the regenerated areas were not indirectly affected during construction. In addition, the environmental assessment which is currently being prepared would outline any required mitigation requirements such as fencing off regenerated areas during construction.
2. How will Ausgrid protect the root systems of street trees during construction?
Trenches are generally set back from street trees and outside the tree protection zone but there will be places along the route where the cables will be installed near the kerb line. An arborist assessment will be completed for sections of the route as part of the environmental assessment. In addition, if trees roots are in the road, generally non-destructive digging would be used where required or the trench location may be altered if possible – this would be identified as part of the project’s environmental assessment and the specialist arborist report.