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TL FOUNDATIONS

Fleet Strategy

Document TP. FL 01.02
16/10/2013

TL FOUNDATIONS FLEET STRATEGY
© Transpower New Zealand Limited 2013. All rights reserved.

TL Foundations Fleet Strategy
TP.FL 01.02
Issue 1
October 2013

COPYRIGHT © 2013 TR ANSPOW ER NEW ZEAL AND LIMITED . ALL RIGHTS
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Any breach of the above obligations may be restrained by legal proceedings seeking remedies including injunctions, damages and costs.

TL FOUNDATIONS
© Transpower New Zealand Limited 2013. All rights reserved.

TL Foundations Fleet Strategy
TP.FL 01.02
Issue 1
October 2013

Table of Contents
EXECUTIVE SUMMARY ...................................................................................................................... 1
SUMMARY OF STRATEGIES .............................................................................................................. 3
1 INTRODUCTION ....................................................................................................................... 5
1.1 Purpose ................................................................................................................................. 5
1.2 Scope .................................................................................................................................... 5
1.3 Stakeholders ......................................................................................................................... 5
1.4 Strategic Alignment ............................................................................................................... 6
1.5 Document Structure .............................................................................................................. 6
2 ASSET FLEET .......................................................................................................................... 7
2.1 Asset Statistics ...................................................................................................................... 7
2.2 Asset Characteristics .......................................................................................................... 10
2.3 Asset Performance .............................................................................................................. 17
3 OBJECTIVES .......................................................................................................................... 20
3.1 Safety .................................................................................................................................. 20
3.2 Service Performance ........................................................................................................... 20
3.3 Cost Performance ............................................................................................................... 21
3.4 New Zealand Communities ................................................................................................. 21
3.5 Asset Management Capability ............................................................................................ 21
4 STRATEGIES.......................................................................................................................... 24
4.1 Planning .............................................................................................................................. 24
4.2 Delivery ............................................................................................................................... 34
4.3 Operations ........................................................................................................................... 35
4.4 Maintenance ........................................................................................................................ 37
4.5 Disposal and Divestment .................................................................................................... 42
4.6 Capability............................................................................................................................. 42
4.7 Summary of RCP2 Fleet Strategies .................................................................................... 45
APPENDICES ..................................................................................................................................... 47
A GRILLAGE EXAMPLES .......................................................................................................... 48
B FOUNDATION CONDITION CODES ..................................................................................... 50
C GRILLAGE ENCASEMENT MODELLING .............................................................................. 53

TL FOUNDATIONS
© Transpower New Zealand Limited 2013. All rights reserved.

TL Foundations Fleet Strategy
TP.FL 01.02
Issue 1
October 2013

EXECUTIVE SUMMARY
Introduction
The condition and performance of tower and pole foundations is essential to the structural
integrity of transmission lines, and to ensuring reliability of supply to customers, and
maintaining public safety.
Our asset management approach for foundations seeks to maintain them in perpetuity, at
least lifecycle cost, and ensure the integrity and reliability of tower structures and the
conductors they support. We have long term programmes of work in progress to encase
deteriorated grillage foundations and maintain the asset health of foundation components.

Asset Fleet and Condition Assessment
The transmission line network includes approximately 25,000 structures that are supported
by foundations.
Most of our foundation fleet is used to support steel lattice towers, but we also have a small
number of monopole foundations and special types of foundations used in riverbeds. The
two main types of foundations supporting steel lattice towers are steel grillage and concrete
plug.
Our foundations are designed to withstand severe climatic loading conditions, and we
monitor and maintain them to ensure satisfactory performance. Structural failures of
foundations are rare, with only 12 recorded since 1963. These failures are usually associated
with extreme weather events.
Our condition assessment programme monitors and records the condition of foundations.
We forecast the future condition of each foundation based on its current condition and our
knowledge of the expected rate of degradation at each location. The forecast of future
condition provides the basis for asset management decision making.
Our condition assessment programme is risk-based, and the intervals between inspections
are adjusted based on the condition of the foundation and its criticality. Assessments are
performed more frequently as the foundation condition approaches the replacement
criteria. Foundations located in unusually aggressive environments, or deemed to be highly
critical, either to the Grid or for safety reasons, are also assessed more frequently.
Foundations include grillage types, consisting of steel buried in the ground, to which tower
footings are attached. Grillage foundations were widely used until the late 1960s, and
support about one half of our steel lattice towers. Buried steel grillage foundations are
subject to below-ground corrosion, leading to risk of foundation failure and subsequent
tower failure with consequent safety, environment and network performance impacts.
Overall, our foundation assets are in reasonable condition, reflecting recent work to encase
our ageing fleet of steel grillage foundations. The average age of the fleet of steel grillage
foundations is 57 years, while the average age of the entire foundation fleet is 44 years.

Foundation Strategies
The main strategy for the foundations asset fleet is the condition-based encasement of
deteriorated steel grillage foundations. Inspections carried out to date show that some of
our grillage foundations have deteriorated to the point where refurbishment is needed to

TL FOUNDATIONS FLEET STRATEGY
© Transpower New Zealand Limited 2013. All rights reserved. Page 1 of 58

TL Foundations Fleet Strategy
TP.FL 01.02
Issue 1
October 2013
keep them in satisfactory condition, and to avoid them declining to a point where tower
propping and major steel work replacement is required.
Since the mid-2000s, 1,700 grillages have been ‘converted’ to concrete over grillage
foundations by encasing them in concrete. A long-term programme of grillage encasement
work is now in place. We intend to refurbish foundations at 400 towers each year
throughout RCP2. Most expenditure identified in this strategy is for this refurbishment work.
The rest of the expenditure planned during the RCP2 period relates to repair of tower
baseplates and below-ground stubs that have corroded to the point where remedial work is
required. The plan involves refurbishing corroding foundation components at 630 sites each
year over RCP2.
A smaller amount of expenditure is allocated to the strengthening of existing undersized
foundations. The plan involves investigating foundations at 40 towers each year and
strengthening 8 each year over the RCP2 period.

Improvements
In our planning for the RCP2 period, we have made a number of improvements to the asset
management of foundations, including:
 improved modelling of condition degradation
 introduction of Asset Health Indices (AHI) to allow better comparison of asset
condition across fleets
 using asset criticality as an important factor in planning foundation asset works – in
particular refurbishments
 planning decisions that consider the whole-of-life cost of foundation assets, covering
Planning, Delivery, Operations, Maintenance and Disposal, as well as their impacts
on other assets, such as towers and poles
 using updated and more detailed building blocks for cost estimates.
For the grillage fleet, our approach remains unchanged from the RCP1 period.
Further improvements will include:
 refinement of condition assessment techniques and asset health models
 refinement of the asset criticality framework.

TL FOUNDATIONS FLEET STRATEGY
© Transpower New Zealand Limited 2013. All rights reserved. Page 2 of 58

generally by concrete encasement.1m A number of bridge replacements are required on access corridors to maintain access to the transmission lines and structure foundations. The strategy is to refurbish. Page 3 of 58 .2m. Grillage refurbishments extend the life of grillages and reduce the chance of foundation failure. All rights reserved. or $51m over RCP2. The strategy is to replace bridges to ensure continuing safe and efficient access to transmission lines for maintenance and project works. Well maintained access tracks are essential to allow safe access to transmission line assets when responding to faults or performing routine inspections and maintenance. TL Foundations Fleet Strategy TP. Undersized Foundation Strengthening RCP2 Cost $4. all grillages that currently have a condition assessment of less than 30 by 2020. The plan involves 64 bridge replacements over RCP2. tower structure collapses and conductor drops.4m Poor design process used for foundations constructed before 1983 has led to the occasional installation of undersized bored concrete foundations. The plans will involve refurbishing approximately 400 grillages each year at an annual cost of $10. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. The plan involves investigating foundations at 40 towers each year and strengthening 8 each year over RCP2. Strengthening undersized foundations reduces the chance of tower structure collapse (with significant implications for safety and reliability). The strategy is to strengthen undersized foundations in all critical locations to minimise the risk of tower failure due to overloading. Capital Expenditure Grillage Refurbishments RCP2 Cost $51m A large number of grillages are deteriorating due to their age and environment. grillages should be encased in concrete before the condition gets too poor (condition assessment less than 40) and it becomes necessary to prop the tower and replace steelwork at significant cost. Bridge Replacements RCP2 Cost $6.FL 01. and ensure no grillage foundation has a condition assessment of less than 40 by 2033 (in 20 years). Ideally.02 Issue 1 October 2013 SUMMARY OF STRATEGIES The following summaries include the main strategies and their respective costs during the RCP2 period (2015/16–2019/20).

This refurbishment is based on the minimum condition assessment score of the four leg-based codes collected at each site. TL Foundations Fleet Strategy TP. The typical threshold is condition assessment 50 before any significant rusting or loss of section is apparent.5m A large number of ageing foundation components are deteriorating. Page 4 of 58 . All rights reserved.5m. Component refurbishments reduce the chance of foundation failure and tower structure collapse (with significant implications for safety and reliability).FL 01. The strategy is to refurbish corroding baseplates. Further detail on the above RCP2 strategies and discussion of the remaining strategies can be found in chapter 4. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. anchor bolts and cast-in stubs prior to onset of significant rusting.02 Issue 1 October 2013 Operating Expenditure Component Refurbishments RCP2 Cost $17. The plan involves refurbishing corroding foundation components at 630 sites each year over RCP2 at an overall cost of $17.

Operations. Performance and Projects)  regulatory bodies: Commerce Commission. Electricity Authority. This document has been developed based on good practice guidance from internationally recognised sources. maintain and operate New Zealand’s high-voltage electricity transmission network (‘Grid’) including the foundations that support conductor-bearing structures (towers and poles). stakeholders. Page 5 of 58 . 1. This includes objectives for future performance and strategies being adopted to achieve these objectives. including distribution network businesses and generators. build. and strategic alignment of the foundations fleet strategy. scope.3 Stakeholders Correct operation and maintenance of foundations is essential for the safe and reliable transport of electricity from generators to customers and distribution networks across public and private land. local and regional Councils. 1. The purpose of this strategy is to describe our approach to lifecycle management of our transmission tower and large pole foundation assets on the Grid. 1. All rights reserved. and the Environmental Protection Authority  Department of Conservation  service providers  customers.2 Scope The scope of the strategy includes the foundations of towers and non-direct buried poles. TL Foundations Fleet Strategy TP.1 Purpose We plan. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. and limited to:  grillage foundations (direct buried grid of steel)  concrete foundations with cast-in tower legs  concrete foundations with cast-in anchor bolts and tower/pole baseplates  large piled foundation structures (typically at river crossings and estuaries)  driven piles and wailings used for mounting poles in riverbeds. and Maintenance. The strategy sets the high-level direction for fleet asset management activities across the lifecycle of the fleet.FL 01. These activities include Planning. Key stakeholders include:  landowners  relevant Transpower Groups (Grid Development.02 Issue 1 October 2013 1 INTRODUCTION Chapter 1 introduces the purpose. including BSI PAS 55:2008. Delivery.

The strategy directly informs the portfolio asset management plans. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. TL Foundations Fleet Strategy TP. Corporate Objectives & Strategy Asset Management Policy Asset Management Strategy Lifecycle Strategies Planning Delivery Operations Maintenance Disposal Foundations Strategy Foundations Plan Figure 1: Position of this Strategy within the Transpower Asset Management Hierarchy 1. and higher-level asset management objectives and targets. characteristics and their performance.4 Strategic Alignment A good asset management system shows clear hierarchical connectivity or ‘line of sight’ between the high-level organisation policy and strategic plan. Chapter 2 provides an overview of transmission line foundations including fleet statistics. This hierarchical connectivity is represented graphically in Figure 1.5 Document Structure The rest of this document is structured as follows. Appendices are included that provide further detailed information to supplement the fleet strategy. Chapter 3 sets out asset management related objectives for the assets.02 Issue 1 October 2013 1. Chapter 4 sets out the fleet specific strategies for managing the assets. and the daily activities of managing the assets. Page 6 of 58 . This document forms part of that line of sight by setting out our strategy on the foundations asset fleet. These strategies provide medium-term to long-term guidance and direction for asset management decisions and will support the achievement of the objectives in chapter 3. These objectives have been aligned with the corporate and asset management policies. All rights reserved. It indicates where this fleet strategy and plan fit within the asset management system.FL 01.

2. asset criticality.FL 01.000 transmission line support structures (such as towers and direct buried poles). maintenance requirements and interaction with other assets  asset performance – including reliability. 2. age profile. safety and environmental and identification of risks and issues.1 Asset Statistics This section outlines the foundations asset fleet population. asset condition. Page 7 of 58 .000 route km of transmission line. Foundations vary in size and type depending on the design loads. which in turn support conductors. 2. The quantities of each type (along with descriptions) are shown in Table 1.000 foundation-supported structures on the network (such as towers).1. Foundations play an important role on the Grid by supporting transmission line towers and poles. More than half of all tower foundations are original buried steel grillage foundations that are subject to corrosion. along with the diversity and age profiles of the physical assets. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. TL Foundations Fleet Strategy TP. This results in an increased risk of foundation and subsequent tower failure. All rights reserved.2 Fleet Diversity Asset fleet diversity is an important asset management consideration. As at 30 June 2012. there are approximately 25.1 Asset Population The Grid is made up of approximately 12. soil type and the preferred construction practices of the day. and spares  asset characteristics – including safety and environmental considerations. diversity. asset health.02 Issue 1 October 2013 2 ASSET FLEET Chapter 2 describes the asset fleet with a focus on:  asset statistics – including population. It is important to maintain these in an appropriate condition through timely maintenance and refurbishment.1. supported by approximately 41.

essentially all foundations have been constructed with a concrete pile/plug and cast-in stub leg. Since then. some 6. Page 8 of 58 . They were the preferred foundation type until the late 1960s when concrete foundations were introduced. TL Foundations Fleet Strategy TP.DIVERSITY GRILLAGE (50%) CONCRETE OVER GRILLAGE (7%) CONCRETE PLUG. All rights reserved. Buried steel grillage foundations are the oldest type of tower foundation on the Grid and comprise more than half of all tower foundations.02 Issue 1 October 2013 Foundation Type Description Population Towers Steel Grillage Grillages that have not yet been refurbished 12. FOUNDATIONS. There are a large number of buried steel grillages in service that were installed up until the late 1960s which are deteriorating due to their age and environments. This type of foundation and connection was installed between the mid-1960s and the late 1970s. The proportion of concrete foundations will increase over time as new lines are constructed. lines are divested or decommissioned and grillages are encased with concrete.FL 01.3 Age Profile Foundation assets have been installed progressively since the 1930s. Figure 2 depicts the diversity of the asset fleet. BORED OR DUG (40%) OTHER TOWER FOUNDATIONS (3%) POLE FOUNDATION (1%) Figure 2: Foundations – Diversity 2.1.667 Concrete Plug (bored dug) Currently preferred foundation type 9. yet the bulk of the population are aged between 45 and 90. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.971 Includes foundation types such as:  Driven Pile with Pile Cap – generally only used at Other river crossings or sites with very poor soils 653  Pad and Chimney – occasionally used at sites with poor soils  Raft and screw pile type foundations Poles Driven Pile and Wailings For mounting poles in riverbeds 272 Total 24.350 Concrete over Steel Grillage Refurbished grillage foundations (by encasement in concrete) 1.500 towers have baseplate and anchor bolt connections. Of the concrete foundations.913 Table 1: Foundation Types and Populations as at 30 June 2013 The type of foundation used has varied with time. Over 600 grillage foundations were refurbished by re-galvanising between 1992 and 2008 and are treated as being new from that date.

500 1. FOUNDATIONS . All rights reserved. Life expectancy should be interpreted as the period after which the risk of failure is deemed unacceptable.Age Profile Foundation life expectancy The life expectancy for each type of foundation is shown in Table 2.AGE PROFILE GRILLAGE CONCRETE OVER GRILLAGE CONCRETE PLUG. on average. an expected 120-year life extension with correct maintenance in place. BORED OR DUG OTHER POLE FOUNDATION 1.02 Issue 1 October 2013 The age profile of the foundation fleet is shown in Figure 3. weather exposure. and construction quality.2.Other 27 50 Timber or steel piles driven into riverbeds foundations Table 2: Foundation Life Expectancy TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. Foundation Type Average Age Life Expectancy Comment Grillage 57 70 Varies from 50 to over 100 years Concrete over grillage 3 120 As for concrete plug Concrete plug. not age (see subsection 2.FL 01.000 500 0 0 10 20 30 40 50 60 70 ≥80 AGE (YEARS) Figure 3: Foundations . Page 9 of 58 . The actual life will depend on the specific site. TL Foundations Fleet Strategy TP. This achieves. One of the fleet’s main strategies relates to the effective replacement of grillage foundations through concrete encasement.3). bored or Assumes concrete/steel interface is maintained 36 120 dug periodically Other – Driven pile with Generally in more aggressive environment than 37 120 concrete pile cap standard concrete plug Other – Pad and 28 120 As for concrete plug chimney Other . works are always planned based on actual condition. It is based on observed life and typical condition degradation rates for each foundation type. While age is of interest for predicting future needs.

2. Page 10 of 58 . and is higher in urban environments and over busy roads than in back country rural environments. Prevention of tower failure Foundation failure leading to a tower failure and conductor drop is a significant safety consideration with risk of electrocution.1 Safety and Environmental Considerations We are committed to ensuring that safety and environmental risks are minimised at all times. Further information on the asset criticality approach is provided in the document ‘Asset Risk Management – Criticality Framework’. The risk is clearly dependant on land use.2 Asset Characteristics The foundations asset fleet can be characterised according to:  safety and environmental considerations  asset criticality  asset condition  asset health  maintenance requirements  interaction with other assets. Regular condition assessments and a robust design process are essential to minimise the risk of foundation failures.02 Issue 1 October 2013 2. particularly when working in sensitive areas such as riverbeds. constraints that would be placed on the rest of the Grid. The methodology considers various aspects that would be impacted by a failure such as load carried.2. These characteristics and the associated risks are discussed in the following subsections. Environmental There is potential for significant environmental impacts when constructing or removing foundations. Environmental issues are mitigated by working closely with the relevant regulatory bodies and landowners and by ensuring compliance with the Resource Management Act 1991 (RMA 1991).2 Asset Criticality Our approach to asset management has been adapted to recognise the differing levels of asset criticality. and the level of redundancy. 2. The most significant safety and environmental consideration for the foundations asset fleet is the prevention of a transmission structure failure. TL Foundations Fleet Strategy TP. Highly critical assets will be designed and maintained to provide a higher level of reliability than less critical assets.FL 01. fire and physical impact damage. A framework has been developed for transmission line assets. the level of reliability required by the customers. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. All rights reserved. 2.

FL 01. All rights reserved. Despite numerous national and international trials. tower line assets are generally assessed every 8 years. soil type and moisture content are all known to influence the grillage condition. the foundation connection 2. If the condition assessments score is less than 50. and will continue to refine and develop this throughout RCP2. the assessment period is reduced to 4 years. The only reliable method of determining the condition of the buried part of the foundation condition is to dig and visually inspect. A separate condition assessment score is recorded for each.02 Issue 1 October 2013 Figure 4 shows the proportion of foundations in each criticality category. FOUNDATIONS - NETWORK CRITICALITY LOW (45%) MEDIUM (39%) HIGH (16%) Figure 4: Foundations – Criticality Approximately half of the foundation asset fleet are classified as medium impact or high impact with respect to network criticality. Sites with a high consequence of failure may be assessed more frequently.2.3 Asset Condition Regular condition assessments on foundations are carried out to assess their condition. Having severely rusting foundations on the network is a major risk that is compounded by the fact that they cannot be readily assessed for condition. We are still at a relatively early stage in the development and application of safety criticality. original galvanising quality. Excavation and inspection (see Figure 5) is relatively TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. New foundation assets are first assessed just prior to the expiration of any defect liability period. in combination with asset health to determine prioritised replacement programmes. Thereafter. Page 11 of 58 .2 discuss how criticality is taken into account. the foundation. The reliability and performance of these assets need to be managed carefully to minimise failure risks. Age. where a score between 91 and 100 is considered as new and 0 is seriously degraded to a point where failure could occur under everyday loading conditions. Grillage foundations Many towers with buried steel grillage foundations are now showing corrosion on tower legs and bracing near the ground line. These assessments produce a condition assessment score. At a condition assessment score of 20. Subsections 2. TL Foundations Fleet Strategy TP. the foundation is incapable of carrying its full design loads.1.2. During regular condition assessments the two locations assessed are: 1. 2.4 and 4. no reliable non-intrusive method has been found to accurately predict which towers have corroded grillages.

Page 12 of 58 . we now use the ground-line interface condition as a proxy for the lower grillage condition. assessing the steel at this depth is disruptive and expensive. in half the cases the grillage was in better condition than the ground interface. For grillage-type foundations the connection is deemed to be the steel from 100mm above ground level to 300mm below. For concrete foundations with bolted connections or cast-in stubs.000 towers have revealed that the extent of corrosion further underground. varies from light to severe. at the grillage level. Analysis of the results shows that in 80% of cases the condition of the grillage is within 10 condition assessment points of the ground-line interface condition.02 Issue 1 October 2013 expensive and also leads to accelerated corrosion. Consequently grillage condition assessment has been carried out on a sampling basis. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. Less than 1.FL 01. Figure 5: Excavated Grillage The bottom of a grillage foundation is typically 2.5 to 3m below ground level.000 towers have had their grillage foundations condition assessed to the base of the grillage. Assessment guidelines for foundations are included in Appendix B. and is within 20 condition assessment points 93% of the time. the connection relates to the steel/concrete interface. Given the high cost and landowner disruption associated with accurately assessing the condition of the buried part of the foundation. As discussed above. All rights reserved. Of the 7% outside 20 condition assessment points. as oxygen will enter into what was a largely oxygen-starved system. TL Foundations Fleet Strategy TP. Excavations undertaken on some 1.

Assessment guidelines for foundations are included in Appendix B. the steel cleaned. Foundation connection components For concrete foundations with bolted connections or cast-in stubs. 1 Using ground-line condition as a proxy for grillage foundations.000 5. Concrete foundations with cast-in stub legs are generally in good condition. All rights reserved. Note that once a grillage foundation is refurbished by concrete encasement. and the area repaired by grouting. the rust does not extend very far into the concrete (<20mm).000 0 0-10 11-20 21-30 31-40 41-50 51-60 61-70 71-80 81-90 91-100 CONDITION ASSESSMENT (CA) SCORE 1 Figure 6: Foundations – Asset Condition Figure 6 shows the distribution of condition assessment codes for foundations. Refurbishment by blasting and painting has proven highly successful. the foundation connection becomes a cast-in stub-type arrangement. In extreme cases a small area of concrete is broken out.02 Issue 1 October 2013 FOUNDATIONS . As for grillages. the connection relates to the steel/concrete interface.000 2. Moisture ingress under the baseplate has subsequently led to corrosion of the anchor bolts and baseplate (which is not visible until the grout is removed). Typically.type foundations is porous and has led to mortar crumbling.000 4. BORED OR DUG OTHER 6. TL Foundations Fleet Strategy TP. but an increasing number are starting to corrode at the concrete and steel interface. Page 13 of 58 .400 (or 11%) of grillage foundations are at or below condition assessment 30. a large number of foundation connection components are deteriorating due to their age and environment.FL 01.000 3.CONDITION GRILLAGE CONCRETE OVER GRILLAGE CONCRETE PLUG.000 1. The majority of the fleet has a condition assessment score of above 40 although approximately 1. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. Poor quality dry-pack mortar originally used under baseplate.

4 Asset Health The AHI reflects the forecast remaining life for any given asset – in effect. The AHI is calculated using:  the current condition of the asset  the age of the asset  the typical degradation path of that type of asset  any external factors that affect the rate of degradation. Asset health information is used in combination with asset criticality data to assign an overall priority to each asset. Foundation component refurbishment is based on the minimum condition assessment score of the four leg-based codes collected at each site.000 0 0-10 10-20 20-30 30-40 40-50 50-60 60-70 70-80 80-90 90-100 CA SCORE Figure 7: Components – Asset Condition Figure 7 shows the condition of foundation components.CONDITION BASEPLATE / ANCHOR BOLT CAST IN SITU STUB LEG 3. such as proximity to the coast. major intervention is required.000 2. or is uneconomic). All rights reserved. it is an assessment of current and future asset ‘fitness for purpose’. and so affect the rate of corrosion of steel towers. For transmission line foundations.FL 01. At this point. such as total replacement of the asset or refurbishment that significantly extends the original design life. 2. The AHI forecast of remaining useful life is based on modelling deterioration or risk that cannot be addressed by normal maintenance (where maintenance to address the deterioration or risk is not possible/practical.000 1. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. Assessing asset health is particularly important as it is used to understand the deterioration profile of asset fleets and to forecast and prioritise replacement and refurbishment activities. Asset health indicators provide a proxy for the probability of failure in asset risk management analysis. More details on our asset health methodology are set out in the document ‘Asset Risk Management – Asset Health Framework’. which is used to optimise the level of investment in the fleet.02 Issue 1 October 2013 FOUNDATION COMPONENTS . this is when the foundation can no longer be relied upon to carry its design loads. TL Foundations Fleet Strategy TP. The typical threshold is condition assessment 50 before any significant rusting or loss of section is visible.2. Page 14 of 58 . We are still at a relatively early stage in developing and applying asset health indicators.

CA 30 has been selected for grillages to account for the uncertainty regarding their below-ground condition. Page 15 of 58 . As an example. Asset Health Decreasing Increasing Criticality Figure 8: Prioritisation Approach Asset health for the foundation fleet has been calculated assuming replacement criteria at a condition assessment score of 20 for all foundations except grillages where replacement is modelled at CA 30. Note: maintenance works such as refurbishment of baseplates and anchor bolts must be carried out periodically to achieve these predicted lives (as noted in Figure 9). which is used to optimise the level of investment in the fleet. All rights reserved. FOUNDATIONS.ASSET HEALTH (12/13) 12+ YRS (90%) 7-12 YRS (4%) 2-7 YRS (3%) 0-2 YRS (0%) NOW DUE (6%) Figure 9: Foundations – Asset Health Indices The greatest asset management challenge for the ageing fleet of foundations is managing the corrosion of buried steel grillages. a number of ageing foundations have a relatively poor condition. there is a slight increase in the risk of failure. A linear degradation rate from the original installation date to the most recent condition assessment score is assumed.2. As the condition assessment score reduces below 20. ground-line interface condition has been used as a proxy for grillage condition as discussed in subsection 2. TL Foundations Fleet Strategy TP. ‘Now Due’ grillages with a condition assessment score under 30 are a higher priority than a high criticality site just reaching 40.FL 01. 2 Literature on in-ground corrosion of galvanised steel suggests the corrosion rate is roughly linear while galvanising is still there. While the overall health of the tower foundations is generally good. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. the better our understanding in this area will be.2 For grillages. but may actually decrease once corrosion starts. due to the heightened risk of them failing.02 Issue 1 October 2013 The association of asset health to the probability of failure is not strongly formed until a condition assessment score of 20 or below is recorded. The manner in which asset health is taken into account in the management of the assets is described further in chapter 4. the failure risk changes very little. the risk of failure increases markedly. Asset health information is used in combination with asset criticality data to assign an overall priority to each asset. Below a score of 30. The more replacements we do. Between a score of 100 and 30.3 above. Figure 8: shows that prioritisation is based on a combination of condition (remaining life) and criticality.

02 Issue 1 October 2013 2. which are programmes of works (essentially made up of small projects) used to address repetitive issues identified through preventive maintenance or fault responses.2. TL Foundations Fleet Strategy TP. Page 16 of 58 . All rights reserved. Contributing factors include:  severely damaged foundations  geotechnical risks due to slips. Repair jobs are raised in the Maintenance Management System and the maintenance contractors are responsible for carrying out this work.5 Maintenance Requirements This subsection describes the maintenance requirements of the foundation fleet. The main purpose of the patrols is to identify defects and sites with very high safety criticality that may then be patrolled more frequently. condition assessments are carried out on a cyclic basis and entail a detailed inspection of the structure and span. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. condition assessments . As discussed in 2. Each year a number of sites require stabilising work and repairs to avoid failure. repairs  Maintenance Projects. In extreme cases a structure may be relocated. including: . servicing  corrective maintenance. Detailed maintenance requirements are included in the relevant service specification documents. The most common fault response and repair work required for foundations relate to foundation failures due to land subsidence or rapid soil erosion. Corrective maintenance Typical maintenance activities for foundations include removing soil and vegetation from the top of concrete foundations and installing protection works such as rip rap in rivers. The most common types of maintenance carried out on lines assets are:  preventive maintenance. In addition. scouring and subsidence  third party excavation or construction around tower foundations. including: . fault response . The Maintenance Lifecycle Strategy provides further details on our approach to the above maintenance works. Preventive maintenance Line patrols are generally performed once a year on every transmission line asset. A ground-based patrol visits each structure/span and walks the conductor line.FL 01. These requirements have informed the maintenance strategies discussed in section 4. we periodically undertake maintenance projects. to visually identify any defects.2.4. The assessment produces a condition assessment score for various components and a defect list. if possible. A patrol report identifies defects required to be rectified.3.

FL 01. Page 17 of 58 .6 Interaction with other Assets The foundations programme is closely aligned with conductor and tower works.3. 2. Towers supporting a line being supplied with a new (or refurbished) conductor may require foundation strengthening due to heavier conductors and higher tension being used. as any new tower work requires foundation work.9m Table 3: RCP1 Spend on Maintenance Projects 2. only one tower foundation failure has occurred and was due to river washout.3. Maintenance jobs are typically run as a project where there are operational and financial efficiencies from doing so.1m $6. mitigating safety and environmental risks. Since 2005. The drivers for maintenance projects include asset condition. All are subject to corrosion.3. and to improve performance.4. This constitutes a RCP2 strategy and is discussed in more detail in subsection 4. the steel at the concrete interface of cast-in in situ foundation legs is painted prior to significant rusting. Similarly. All rights reserved.1 Reliability Achieving an appropriate level of reliability for our asset fleets is a key objective as it directly affects the experience of our customers. Five failures were caused by land movement or river scour. The refurbishment of corroded steel and the replacement of mortar prior to significant degradation in baseplate and anchor bolt foundations are carried out to ensure that structural integrity is maintained. 2.02 Issue 1 October 2013 Maintenance projects Maintenance projects typically consist of relatively high-value planned repairs or replacements of components of larger assets.4.1.8m $2. TL Foundations Fleet Strategy TP. land movement and washout do occur. with established modern design practices the probability of foundation failure is low. Historic spend – maintenance projects Table 3 provides an overview of historic maintenance project expenditure. While foundation failures due to extreme climatic loading. These integration processes are managed through the Integrated Works Planning (IWP) processes discussed in subsection 4. Project 2009/10 2010/11 2011/12 Total Various $2. those with baseplates and anchor bolts and those with cast-in stubs.0m $2. Examples of past maintenance projects are set out below. Maintenance projects would not be expected to increase the original design life of the larger assets. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.3 Asset Performance This section describes the historic performance of foundation assets and any associated risks and issues. Connection component refurbishments Foundation connection components comprise two types. Reliability is measured primarily by the frequency and length of outages. In this instance. Since 1963 there have been 12 foundation failures.2. Future maintenance projects are discussed in subsection 4. conductors were transferred to a temporary structure prior to the foundation (and tower) failure.3. the remaining seven were due to high wind events pulling the foundations from the ground.

as we work closely with authorities and landowners to mitigate any adverse effects associated with our works. property or the Grid. Age profiles Grillage foundations are the oldest type of foundation.3 2. We maintain a register of problematic areas and at-risk structures are monitored after major weather events. with priority given to sites whose failure would pose significant risk to people. condition assessments and line patrols identify foundation issues before towers fail. A slight conservative approach is therefore warranted. Structures with concrete pile foundations built before 1983 continue to be investigated. Age-based deterioration is the major driver of the work programme related to this asset fleet.3. ITOMS considers overall transmission line performance (not on an asset type basis. suggest that under-strength foundations still exist in some cases. compounded by the fact that foundations buried at depth cannot be readily condition assessed. This overall performance is considered in the Conductors and Insulators fleet strategy. Undersized foundations Studies have revealed that concrete foundations built before 1983 were usually designed based on very limited soil testing and with assumptions made about soil properties. Page 18 of 58 . Recent studies. with the bulk of the fleet now aged between 45 and 90. however there is a risk that the condition of any buried grillage is worse than predicted.4 Risks and Issues This subsection briefly discusses risks and the identified issues relating to the foundation asset fleet. 2. Our environmental record is considered to be very good. All rights reserved. including full-scale foundation testing. such as tower foundations).3. The risks associated with foundation corrosion include rapidly increasing costs to maintain if left too late and reduced structural strength that could lead to foundation and tower failure. TL Foundations Fleet Strategy TP.3 Performance Benchmarking International Transmission Operations & Maintenance Study (ITOMS) involves performance comparisons (including reliability) between 27 utilities.3. Limited effectiveness of near-surface visual inspections Severely rusting foundations on the network present a major risk. 2. 3 Details can be found in the Conductors and Insulators fleet strategy. Some below-ground sampling has been carried out to inform the asset management approach.FL 01.02 Issue 1 October 2013 In many instances. Approximately 10% of grillages and foundation components are now corroded to the point of requiring replacement or refurbishment.2 Safety and Environmental Performance No people have been harmed by any foundation failure on our network. leading to undersized foundations occasionally being installed. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.

All rights reserved.FL 01. These events can cause fire on public or private land. fatalities and injuries from electrocution or impact of falling objects. We maintain a register of problematic areas. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. property damage and loss of power supply. Page 19 of 58 .02 Issue 1 October 2013 Foundation failure Foundation failures can result in tower collapses and conductor drops. TL Foundations Fleet Strategy TP. Washouts and landslides Poor slope stability and/or river scouring have been significant causes of foundation failures. Maintenance managers and contractors monitor at-risk structures after major weather events.

Our overarching vision for our foundations fleet is to maintain them in perpetuity. 3.1 Safety We are committed to becoming a leader in safety by achieving injury-free workplaces for our employees and to mitigate risks to the general public. We have specified our network performance in terms of Grid Performance (reliability) and Asset Performance (availability) in our Asset Management Strategy. Safety is a fundamental organisational value and we consider that all incidents are preventable. . and we will work towards these being formally linked in the future. The current rate is 1.4.2 Service Performance Ensuring appropriate levels of network performance is a key underlying objective. Grid Performance objectives state that a set of measures are to be met for GXPs based on the criticality of the connected load. Recognising the reduced level of control we have in relation to public safety. and to ensure the integrity and reliability of tower structures and the conductors they support. No major failure of foundation assets with high or very high safety criticality. at least lifecycle cost. Chapter 4 discusses the strategies to achieve them. In addition Asset Performance objectives linked to system availability have also been defined. Further objectives in the following areas have been defined:  Safety  Service performance  Cost performance  New Zealand communities  Asset management capability. As described in section 1. 3. Page 20 of 58 .2 every 5 years. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. All rights reserved. we will take all practicable steps to ensure transmission line assets do not present a risk of serious harm to any member of the public or significant damage to property. TL Foundations Fleet Strategy TP. Service Performance Objectives for Foundations .FL 01. Less than 1 foundation failure every 5 years. These high-level objectives are supported by a number of fleet specific objectives. and higher-level asset management objectives and targets as set out in the Asset Management Strategy. Safety Objectives for Foundations .02 Issue 1 October 2013 3 OBJECTIVES Chapter 3 sets out asset management objectives for transmission line foundations. Zero injuries caused by foundation failures. These objectives are set out below. these objectives have been aligned with the corporate objectives.

we have set out a number of maturity and capability related objectives. We are committed to implementing systems and decision- making processes that allow us to effectively manage the full lifecycle costs of our assets. such as erosion and sediment control during site works.3 Cost Performance Effective asset management requires optimising lifecycle asset costs while managing risks and maintaining performance. 3.02 Issue 1 October 2013 3. Minimise cost of works by packaging work into blocks of consecutive structures wherever possible. 3.4 New Zealand Communities Asset management activities associated with the foundation asset fleet have the potential to impact on the environment and on the daily lives of various stakeholders. construct and maintain foundations to minimise lifecycle costs while meeting required levels of performance. . All rights reserved. Cost Performance Objectives for Foundations . .5 Asset Management Capability We aim to be recognised as a leading asset management company. To achieve this. . These objectives have been grouped under a number of processes and disciplines that include:  Risk Management  Asset Knowledge  Training and Competency  Continual Improvement and Innovation. . TL Foundations Fleet Strategy TP. No damage to third party property due to foundation failures. Improved efficiency through extension of the planning horizon. . Disestablished site foundations should be re-instated to their former natural forms to allow the land to recover. Design. Minimise cost of capital projects through long-term resource planning of service providers. The rest of this section discusses objectives in these areas relevant to the foundation asset fleet. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. Page 21 of 58 . . . Minimise stakeholder disruption by packaging work into blocks of consecutive spans wherever possible.FL 01. Compliance with RMA 1991 requirements. Relationships with landowners and communities are of great importance to us and we are committed to using asset management approaches that protect the natural environment. New Zealand Communities Objectives for Foundations . Maintain effective relationship with stakeholders affected by foundation works.

5. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. Improve the condition assessment consistency through improved guidelines (such as photographic examples).02 Issue 1 October 2013 3. We are currently at an early stage of implementing the framework as we work towards formal and consistent integration of asset criticality into the asset management system. based on the criticality framework. Formalise and implement an asset management approach that is differentiated by network and safety criticality. . 3. Finalise and implement the safety and network criticality categorisation systems for foundation applications. . Continuously improve the asset health modelling of foundations. including root cause analysis. Enhance the failure and incident records system to improve consistency and usefulness of data. Asset Knowledge Objectives for Foundations .5. TL Foundations Fleet Strategy TP. including the risk-weighted cost of circuit unavailability (such as the cost of an outage or the increased chance of outage due to reduced redundancy). . Expand knowledge of foundation condition through scheduled condition assessment and analysis of as-found condition during the foundation replacement and refurbishment programme. . . We have commenced this by prioritising fleet replacement expenditure programmes. Relevant asset knowledge comes from a variety of sources.1 Risk Management Understanding and managing asset-related risk is essential to successful asset management.2 Asset Knowledge We are committed to ensuring that our asset knowledge standards are well defined to ensure good asset management decisions. Develop a risk-based model for assessing the trade-offs between different work methods (such as live line techniques). All rights reserved. Asset criticality is a key element of many asset management systems. This asset knowledge must be captured and recorded so that it can be conveniently accessed.FL 01. Risk Management Objectives for Foundations . We currently use asset criticality and asset health as proxies for a fully modelled asset risk approach. including experience from assets on our network and condition information. Page 22 of 58 .

Increase and then maintain the in-house skill base with regard to asset management principles and application. TL Foundations Fleet Strategy TP.5. A large source of continual improvement initiatives will be ongoing learning from our asset management experience.5. All foundation works to be carried out by service providers that are suitably qualified and competent for the specific tasks required.3 Training and Competency We are committed to developing and retaining the right mix of talented. Training and Competency Objectives for Foundations . Page 23 of 58 . Continue to monitor new and emerging foundation technologies and designs.4 Continual Improvement and Innovation Continual improvement and innovation are important aspects of asset management. . TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.FL 01.02 Issue 1 October 2013 3. competent and motivated staff to improve our asset management capability. Continuous Improvement and Innovation Objective for Foundations . 3. All rights reserved.

4. The strategies are aligned with our lifecycle strategies below and the chapter has been drafted to be read in conjunction with them.1.4. All rights reserved. Planning activities Planning activities are primarily concerned with identifying the need to make capital investments in the asset fleet.2. The main types of investment considered in this strategy are enhancement and development. The majority of capital expenditure consists of grillage refurbishment. and replacement and refurbishment works. Capital investment drivers Categories of capital investment generally have specific drivers or triggers that are derived from the condition of the overall system or from individual assets. We support our planning activities through a number of processes. while operating expenditure is mainly covered by section 4. Capital expenditure planned for the period is covered by the strategies in section 4.FL 01. The planning lifecycle strategies for these processes are described in the subsections below. compliance with Grid reliability standards. which is described in subsection 4.  Planning Lifecycle Strategy  Delivery Lifecycle Strategy  Operations Lifecycle Strategy  Maintenance Lifecycle Strategy  Disposal Lifecycle Strategy This chapter also discusses capability related strategies which cover asset knowledge.02 Issue 1 October 2013 4 STRATEGIES Chapter 4 sets out the fleet specific strategies used to manage the foundations asset fleet. technology changes and failure TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. These drivers include demand growth. Page 24 of 58 . training and competence. These strategies provide medium-term to long-term guidance and direction for asset management decisions and will support the achievement of the objectives in chapter 3. Scope of strategies The strategies focus on expenditure that is planned to occur over the RCP2 period (2015– 2020). TL Foundations Fleet Strategy TP. but also include expenditure from 1 July 2013 to the beginning of the RCP2 period and some expenditure after the RCP2 period where relevant. including:  IWP  cost estimation.1 Planning This section describes our strategies relating to the planning lifecycle phase of the foundations fleet and identifies where and how these strategies support the objectives for the overall fleet.1.

Any asset management related costs following their initial installation will be managed through the foundations portfolio.FL 01.2 Replacement and Refurbishment This subsection describes replacement and refurbishment strategies for the foundations fleet.1 Enhancement and Development The most important driver for new foundation investments is the facilitation of new or strengthened towers. to support new structures or to enable upgrading of conductors. where the priority is higher for assets where the consequence of failure is higher. Following completion of the project. which is driven by failure risk. We use condition assessment data gathered during refurbishment programmes to model the condition of grillages that have not yet been refurbished. Page 25 of 58 . foundations that do not comply with current design standards are strengthened. Facilitate line projects Modify existing foundations. to increase reliability. and strengthen other foundations as part of specific enhancement projects. As part of uprating projects. Prioritisation is undertaken on the basis of asset health and asset criticality. System growth projects principally include new greenfield lines or the uprating of existing lines. Refurbishment is expenditure on an asset that creates a material extension to the end of life of the asset. including strengthening and relocation. the cost for such foundation work is currently included in the relevant conductor projects. Specific interventions have been defined for foundations based on their condition and informed by their relative criticality. It does not improve its attributes. All rights reserved. which may require stronger structures and foundations. the costs will be allocated out to the relevant foundation asset.02 Issue 1 October 2013 risk (indicated by asset criticality and health measures). 4 For more details. we will install a number of new tower structures and their associated foundations. enabling better works prioritisation. 4.4 4. which is carried out to ensure that an asset is able to perform its designated function for its normal life expectancy.1. Condition driven projects Foundation replacement and refurbishment works are primarily triggered by asset condition represented by condition assessment score. see the Conductors and Insulators fleet strategy. which is driven by demand  condition of grillages and other foundation components  foundation strengthening and replacements. TL Foundations Fleet Strategy TP. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.1. Specific examples that drive capital investment in foundation assets include:  new line developments or uprating of existing circuits. The tower investments are undertaken to meet expected system growth and to ensure appropriate reliability for customers. These projects drive the need to invest in foundations. Replacement is expenditure to replace substantially all of an asset. This is distinct from maintenance work. In the next few years. The timing and cost of works will be driven by the relevant conductor works. From a planning perspective.

Specifically. Between 1992 and 2008. These interventions and their rationale are set out below. Alternative approaches for grillage refurbishments have been assessed. concrete encasement of the tower legs has become the preferred refurbishment option. Grillage refurbishments – approach Use concrete encasement designs as the preferred refurbishment option wherever they can be installed in a cost effective manner. Since then. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. Most significantly. including lower cost. TL Foundations Fleet Strategy TP. increased performance and reduced requirements for future condition assessment. those options that have been discounted include  Excavate and remove grillages for re-galvanising. Cost is approximately 1. less risk to the structure during installation. In some locations it may be impractical to transport concrete to site.6 times the cost of encasement and we will still be left with buried steel. 5 For more details on encasement costs. simplifying maintenance and condition assessment requirements. Concrete encasement designs have many advantages over buried steel. The proportion of grillage replacements is predicted to be small (under 10%) compared to the number of concrete encasements. and so reducing risk.  Replace with a new grillage designed specifically for the given location – the cost is approximately 1.5 there is no scope for strengthening. see the cost section of the Grillage Refurbishments Programme strategy.4 times that of encasement. and put back in the ground (in another location to allow a rolling programme). and we will still be left with buried steel.02 Issue 1 October 2013 Refurbished foundations will be designed to carry the anticipated design loads of likely future upgrades on the line.FL 01. re- galvanising and replacing them. All rights reserved. over 600 grillage foundations were refurbished by removing. they bring the steel interface above ground. the existing grillage should be refurbished or a new grillage installed. In these instances. Page 26 of 58 .

Investigations have found that many of these buried steel members are severely corroded.000 towers on the network still have grillage foundations — 50% of the foundation fleet. Grillage selected if worst leg condition is CA 40 or below. Grillage may be prioritised again if there reaches CA 40 is only 1 low coded leg with the other 3 significantly better coded. preferably by concrete encasement. In some Concrete encasement locations this is not practical due to the cost or replacement of getting concrete to the site. The actual condition of the grillage fleet for the majority of towers is therefore unknown. All rights reserved. Ensure no grillage foundation has a condition assessment score less than 40 by 2033 (in 20 years). . all grillages that currently have a condition assessment score less than 30. refurbish. Over 12. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. Grillage Condition . Yet grillages cannot be readily condition assessed because they are buried up to 3m below ground. Preference is to complete concrete encasement wherever possible to bring interface issues above ground where they can be managed by non-intrusive inspections and remedial work. Since the mid-2000s. Page 27 of 58 . Where costs of concrete encasement exceed like-for-like replacement by greater than 30%. Concrete Encasement Like-for-Like Replacement Figure 10: Decision process for grillage encasement versus replacement Grillage Refurbishments Programme By the end of the RCP2 period. complete like-for-like replacement. The average grillage age is 57 years.02 Issue 1 October 2013 The flowchart (in Figure 10) outlines the decision process used to decide on concrete encasement or like-for-like replacement. .700 grillages have been ‘converted’ to concrete over grillage foundations by encasing them in concrete.FL 01. TL Foundations Fleet Strategy TP. with some now almost aged 90. Background Grillage foundations are simply galvanised steel members buried underground. This poses a significant risk to the network. 1. .

We have good ground-line condition data for every foundation. Modelling grillage condition As discussed in subsection 2. Page 28 of 58 . Foundations with such members have reached replacement criteria and should be targeted for replacement as soon as possible. Ideally.FL 01. Foundations with a condition assessment score of 30 can be concrete encased without the need for member replacements. At a condition assessment score of 40 the galvanising is gone and there are initial signs of metal loss.5% chance that its condition assessment score is 20 or less.200 structures had their ground-line interfaces refurbished by blasting and applying thermal zinc spray. grillages should be encased in concrete before the condition gets too poor. and a 3. and in 93% of cases it is within 20 condition assessment points. a condition assessment score of 30 to 35 is the optimal time to encase a grillage in concrete. In 80% of cases it is within 10 condition assessment points. with the other half being worse. In the late 1990s and early 2000s approximately 2. As discussed in subsection 2. The model also includes grillage foundations that have had their ground-line interfaces refurbished.2. as such a condition assessment score of 40 is deemed the most appropriate condition to target for encasement. It assumes a linear degradation rate from the original installation date (at condition assessment 100) to the most recent ground-line condition recording. Propping a tower and removing members increases cost significantly. Condition assessment scores less that 30 would require some replacements and more extensive preparation works. All rights reserved. metal loss has certainly occurred. It also increases safety risk to workers and the potential risk of tower failure during the works. because definitive condition information cannot be readily observed. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. Optimum replacement time Foundation members with a condition assessment score of 20 have lost over 10% cross section and cannot be relied upon to carry their design loads.5% chance that a tower with a ground-line interface condition assessment score of 40 may have a grillage condition assessment score between 20 and 30. but the members have not yet reached replacement criteria. Generally. Foundation inspection records for these structures were interrogated to determine the pre- refurbishment condition and inspection date and used to derive the degradation rates for these structures in the model.02 Issue 1 October 2013 Assessing condition The ground-line steel condition can be used as a proxy for the grillage condition provided a somewhat conservative approach is taken with regard to refurbishment or replacement timing. otherwise it will be necessary to replace significant steelwork. then continues linearly to forecast future condition. investigations carried out on close to 1.3.2. TL Foundations Fleet Strategy TP. However. half the grillages were in better condition than the ground-line steel.000 towers have revealed that the condition of the steel near ground-line (100mm above to 300mm below ground) is generally quite similar to that of the more deeply buried steel. This means there is a 6. a conservative approach will be adopted. At a condition assessment score of 30. we have created a model to predict current and future grillage condition. On balance. Their ground- line condition is therefore no longer a good proxy for grillage condition.4.

 Grillage condition assessment score is taken as the worst of the leg interface condition codes. refurbish grillages when they reach a condition assessment score of 40. a further 50 will be refurbished somewhat early. as deliverability constraints and needs for scale efficiency will lead to foundations being addressed differently to that modelled. we will re-evaluate the appropriateness of the chosen plan.FL 01. approximately 3. It is estimated that for every 350 foundations refurbished based solely on condition. Refurbishment volumes of 200 and 300 failed to achieve the grillage refurbishment objectives. Plan to have no grillages with a condition assessment score under 40 within 20 years (2032/33) 3. By 2020 the condition of 880 grillages will fall below condition assessment 30. one key objective is to minimise disruption to stakeholders. At the end of RCP2.  Life expectancy of an encased grillage is 120 years from the encasement date. By that time. Grillage refurbishment objectives and plan Based on available condition information and reflecting the optimum replacement timings. The data for these is somewhat less robust than for non-refurbished sites.400 have a condition assessment score less than 30. it is desirable to refurbish all grillages on a single property at one time. This inevitably means that some works are carried out slightly earlier than they would be if based solely on condition. Page 29 of 58 . Beyond 2033. As an example.02 Issue 1 October 2013 The following assumptions are used within the grillage condition model. The plan is therefore to refurbish foundations at 400 towers each year throughout RCP2.000 grillages are predicted as having condition assessment score below 40. however they do pose a risk. As of June 2013. However. based on condition data gathered from the previous 10 years. it can be expected that the original installation date. 6 For the first objective the minimum required numbers are (1400 + 880)/7 years = 326/year. soil conditions and construction are effectively equivalent at each property. in general. Modelling (see Appendix C) has determined that 350 grillage encasements each year is the optimum volume for the programme to achieve the above objectives.000 grillages will fall below 40. All rights reserved. Condition assessment data of the excavated steel will be collected while refurbishing the grillage foundations. TL Foundations Fleet Strategy TP.  Degradation rate is linear. the following condition-based objectives have been developed: 1. Of these 1. the youngest original grillage will be almost 80. all grillages will have been refurbished by 2045. Over the next 20 years the condition assessment score of an additional 4. They will be targeted for refurbishment before the end of RCP1 period. while for the second objective the minimum required numbers are (3000 + 4000)/20 year = 350/year TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. To achieve this. Plan to have no grillages with a condition assessment score under 30 by end of RCP2 (2019/20) 2. There is a small number predicted to have a condition assessment score less than 20: these are all at sites where interface refurbishments were carried out. If the programme continues at 400 grillages each year.6 It should be noted that 350 grillage encasements each year represents an ideal result.

02 Issue 1 October 2013 Grillage prioritisation Prioritisation will be based on the priority matrix (see Figure 8).4 for further details). TL Foundations Fleet Strategy TP.1. the average unit cost of a grillage encasement is $25.FL 01. due to the heightened risk of them failing. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.2m. All rights reserved.ASSET HEALTH FOUNDATIONS .000 1.500 2. The assumptions made in estimating unit costs include:  impact of historic project risks are captured by out-turn unit costs 7 This shows the effect of refurbishing 350 grillages each year of the worst-condition grillages. Grillages with a condition assessment score under 30 are a higher priority than a high-impact grillage just reaching 40. Impact of refurbishment programme Figure 11 shows the predicted impact of the encasement programme on the number of at- risk grillage foundations.000. which balances condition and criticality.500 1.DO NOTHING) 12+ YRS (91%) 12+ YRS (79%) 7-12 YRS (5%) 7-12 YRS (5%) 2-7 YRS (4%) 2-7 YRS (4%) 0-2 YRS (0%) 0-2 YRS (2%) NOW DUE (0%) NOW DUE (10%) Figure 12: Foundation Asset Health Forecast Programme cost Cost and scope estimation for grillage refurbishment works is an example of volumetric forecasting (see Planning Lifecycle and subsection 4. To complete approximately 400 grillages each year will cost an estimated $10. GRILLAGES AT OR BELOW CA 40 CA 31-40 CA 0-30 3.PLAN) (19/20 . Page 30 of 58 . To date.ASSET HEALTH (19/20 .000 2.500 3.000 500 0 12/13 13/14 14/15 15/16 16/17 17/18 18/19 19/20 7 Figure 11: Grillage Asset Health Forecast Figure 12 shows the effect of the programme on foundation asset health contrasted with the situation if the grillage encasement programme is not undertaken. FOUNDATIONS .

An annual cost of $880. Undersized foundation strengthening Strengthen undersized foundations in all critical locations to minimise the risk of tower failure due to overloading.2m. This work is required to support safety and reliability by preventing structure collapses due to foundation failures. this equates to a total cost of $2. All rights reserved.000 (including design). which is discussed in subsection 4.000.1. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. Based on 47 pile foundation replacements over RCP2. with an average cost of $105. We will continue to investigate the capacity of existing foundations at critical sites and will strengthen those found to be understrength. Replace/Refurbish Pile Foundations Replace or refurbish pile foundations based on condition.000 to $170. Page 31 of 58 . Over the past 10 years. Similar investigations have been carried out in recent years. Pile foundation replacements for RCP2 are forecast at approximately 9 structures per year addressing condition based replacements and new installations in flood prone river locations. Pile foundation replacement generally focuses on sites susceptible to erosion (where the land is unstable). Studies have revealed that concrete foundations built before 1983 were usually designed based on very limited soil testing and often assumed soil properties. from $25.FL 01. The cost of pile foundations are derived using our volumetric forecasting methodology.4. an average of five pile foundations each year have required replacement. In the 1990s several hundred safety critical sites were investigated. and those in rivers which have degraded to a point where replacement is warranted. Costs to strengthen concrete foundations vary considerably. Urban developments and changing land use continue to increase the safety criticality of numerous sites each year. again resulting in approximately 20% being strengthened.000 at each site. The cost of pile foundation strengthening has been derived using our approach to volumetric forecasting.4.000 has been allowed for each year from 2015 to 2020 for strengthening undersized pile foundations. leading to occasional installation of undersize foundations.1. The plan is to annually investigate foundations at 40 towers and strengthen an average of 8 each year over the RCP2 period. with the number each year being somewhat dependent on natural environmental events. which is discussed in subsection 4.02 Issue 1 October 2013  the building blocks used are sufficiently detailed to reflect typical projects  the proportion of sites with difficult soil conditions will tend toward a constant proportion  the proportion of cost incurred due to access and site topography will tend toward a constant proportion. TL Foundations Fleet Strategy TP. The average out-turn cost for each foundation replacement is $47. with some 20% later being strengthened.

We have adopted a risk-based prioritisation approach that takes into account four factors to prioritise foundation works:  condition (taking due account of any known discrepancies between grillage and interface condition)  asset criticality (in respect to Grid reliability and safety)  existing foundation capacity and whether the foundation should be strengthened  whether other works are required on the same property (minimise landowner disruption). This optimisation approach seeks to ensure that works are deliverable and undertaken in an efficient and timely manner. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. Access routes must be maintained so that. with the scope and cost estimates becoming more accurate as the project becomes more refined.0m. The IWP process integrates capex across a moving window of up to 10 years in the future. The landowners requirements for access and load-bearing capability may be significantly less than ours. TL Foundations Fleet Strategy TP. All rights reserved. Planning of all foundation works takes into consideration relevant site strategies.3 Integrated Works Planning Our capital governance process –IWP – includes the creation of business cases that track capital projects through three approval gates. minimisation of required outages and resources.02 Issue 1 October 2013 Bridge replacements Replace access corridor bridges based on condition. Prioritise foundation works Prioritise the refurbishment and strengthening of foundations taking into account existing condition. as a minimum.1. Page 32 of 58 . 4. and existing bridges may need to be upgraded or replaced to meet our requirements. asset criticality and other factors. Our technical standards for bridges rely on the Transit NZ Bridge Manual.FL 01. the access tracks and bridges can safely support access using conventional 4WD vehicles. and any potential synergies with other projects. we estimate a total expenditure of $6. The main purpose of this strategy is to ensure continuing safe and efficient access to transmission lines for maintenance and project works. Based on a forecast of 64 bridge replacements over RCP2. The average annual expenditure on access track bridge replacements over the last five years is approximately $1. Well maintained access tracks and bridges are essential to allow safe access to transmission line assets when responding to faults or performing routine inspections and maintenance.0m and this is predicted to continue through RCP2. This is particularly the case where the capacity of an existing bridge is a potential constraint on project works such as grillage replacements or conductor stringing.

All rights reserved. See subsection 4. This has now transitioned to the central cost estimation team. In a general sense.1. This enhances safety and reliability. Historically.2 for further details on how this is applied to replacement projects. It ensures that all re-conductored lines and structure foundations on uprated lines where loads are increased comply with current loading and capacity requirements. Assumptions made in using a volumetric costs methodology to achieve P50 include:  the sample size of historic works is sufficiently large to provide a symmetric distribution for the cost  a large number of equivalent projects will be undertaken in future  cost building blocks based on historic out-turn costs capture the impact of past risks  volumetric estimates are to be determined using the Transpower Enterprise Estimation System (TEES) (US Cost) system  scope is reasonably well defined and reflects a predetermined list of ‘standard building blocks applied to all estimates. which uses the cost estimation tool Transpower Enterprise Estimation System (TEES).1. Page 33 of 58 .1. They are categorised as volumetric works for estimation purposes. equivalent historic projects. 4. Cost estimates for volumetric capital projects are developed on the basis of tailored ‘building blocks’ informed by actual cost of completed. Most foundation works are repetitive with similar scopes. This strategy supports delivery of enhancement and development projects discussed in subsection 4. TL Foundations Fleet Strategy TP. This feedback-based process is used to derive average unit costs for future works. P50 is an estimate of the project cost based on a 50% probability that the cost will not be exceeded. cost estimates for foundation works were developed using proprietary systems.1.02 Issue 1 October 2013 Re-assess foundation requirements before re-conductoring or uprating Ensure any work that changes loadings on structures includes a robust design assessment of the foundation strength to ensure compliance with current standards.4 Cost Estimation Cost estimation is a key stage of the capital investment process and forms a critical input into projects at various stages in the planning process. the P50 estimate is based upon an equal chance of project overruns or under runs up to the finalisation of the project scope. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. Further details on our cost estimation approach can be found in the Planning Lifecycle Strategy document. that is. Ensure foundation works are scoped to achieve P50 Ensure foundation project estimates are developed and scoped to achieve P50 cost value.FL 01. The P50 cost value is an estimate of the project cost based on a 50% probability that the cost will not be exceeded. the expected cost of a programme of similar projects is of more interest than the costs of projects that are estimated separately.

see The Sourcing.2.01) specifies higher-return period weather events for critical assets than for less critical ones (such as higher reliability level for more critical assets). the design process8 aims to ensure appropriate site-specific designs are used. concrete plugs with cast-in tower leg stubs are the preferred method for new foundations. the majority of detailed design takes place as part of the delivery cycle.1 Design When applied to foundations.1. Supply & Contracts Approach (2011) and the Delivery Lifecycle Strategy.2 Procurement For more details of our general approach to procurement.FL 01.2. Capex projects move into the Delivery Lifecycle. Where concrete is not easily transportable to a particularly remote location. sustainable asset management planning and delivers on the objectives relating to network and cost performance. There are significant economies of scale in increasing foundation capacity at the same time as undertaking foundation encasement/replacement. Replacement foundation design Design replacement foundations to carry the anticipated design loads of likely future upgrades. again. All rights reserved. as little more time is required to dig a bigger hole. As discussed above in subsection 4. The following discussion focuses on delivery issues that are specific to the foundations fleet. For the grillage replacement option. For concrete encasement. 4. 4. slightly longer grillage members are required.2 Delivery Once planning activities are completed.DL 12. but. TL Foundations Fleet Strategy TP. Designing replacement foundations taking into account anticipated design loads of likely future upgrades is prudent. This is in line with standard international practice. a standard grillage or other foundation type may be considered. Foundation design Ensure assets with high safety or Grid criticality are designed and maintained to be more reliable than less critical assets. Page 34 of 58 . Delivery activities undertaken are described in detail in the Delivery Lifecycle Strategy.02 Issue 1 October 2013 4. 8 While design activities are undertaken during the Planning Lifecycle. Procurement issues relevant to the foundations fleet during the RCP2 period are set out below. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. the installation cost is relatively constant. Our transmission line loading standard (TP. the only additional cost is for extra concrete.2.

Where practicable. and second preference. This strategy aligns with the objective to control costs by minimising supplier diversity. The following discussion focuses on operational issues that are specific to the foundations fleet.3 Operations The Operations Lifecycle phase for asset management relates to planning and real time functions. Project deliverability Ensure planned projects are deliverable within available financial. This strategy aligns with the objectives in relation to cost optimisation and system performance and reliability. All rights reserved. selected tender. In particular. an integrated programme view is taken rather than evaluating the sum of the individual works.3 Delivery Planning The plan for delivering new foundations for new transmission lines and upgraded transmission lines are managed under our IWP process as set out in subsection 4. Our IWP processes deliver on this strategy.2.3. 4. Operational activities undertaken are described in detail in the Operations Lifecycle Strategy. TL Foundations Fleet Strategy TP.02 Issue 1 October 2013 Award contractor work on a sole source ‘yours to lose’ basis. landowner disruption and system outages are minimised. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. This strategy aligns with the objective to minimise system disruptions and maintain reliability.1. Locally based contractors have geographic knowledge of the area and so are more suitable to work in rugged terrain. Selected projects are put out to tender based on the availability of the expertise required to perform the project. 4. Performance-based contracting will be used to provide incentives to contractors to align their objectives with ours.FL 01. Page 35 of 58 . Foundation work is mostly of a volumetric nature. work is packaged to maximise efficiency and ensure that any travel time. Package work Package works into blocks of consecutive structures and ensure multiple works are carried out at one site simultaneously wherever possible. Award contractor work by geographic locations on a sole source ‘yours to lose’ basis. ensuring deliverability of projects planned in line with the IWP processes is essential to support our objectives of controlling costs and achieving the desired asset management outcomes. The preferred procurement method is sole source. Under the IWP processes. labour and material constraints. This subsection sets out how IWP is applied to tower and pole project delivery.

We ensure that asset specific emergency plans are developed for critical assets. This strategy aligns with the stakeholder and network performance objectives.1 Outage Planning Power system outages for preventive maintenance.  Emergency Management Team: Maintain readiness of emergency management team with communications routes to Civil Defence and to site works contractors. corrective maintenance. 4. Maintain contingency response resources Have sufficient plans. When works do require an outage.  Business continuity plan: Maintain the business continuity plan. Planning for failures is essential so that service can be restored relatively quickly when failure occurs. To ensure rapid network restoration times.FL 01. located in many different environments. Foundation works outage planning Plan to minimise disruption to customers for foundation works that require outages. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. including emergency restoration structures. Resources must be sufficient to manage contingencies using a tiered response where local contractors rectify failures of one or two structures. and put in place as required. Page 36 of 58 .2 Contingency Planning With thousands of towers on the network. Continue the business continuity plan. We will follow the strategies set out below when planning outages for foundation assets. All rights reserved. This strategy delivers on the objectives in relation to System Performance and Reliability. TL Foundations Fleet Strategy TP. but may ask others for help following multiple structure failures. Yearly drill for significant outage communications and process. floods and landslides. skilled manpower and emergency spares in place to enable rapid restoration of transmission service following single or multiple structure failure(s) or conductor drop(s). we employ the following contingency strategies. and replacements must be planned to minimise disruption to customers. it is inevitable that foundations and their towers will occasionally fail during extreme events such as high winds. Grid operations identify requirements for outages (including reclose blocks) and manage the planning of outages and reclose blocks.3. including emergency restoration structures.02 Issue 1 October 2013 4.3. we coordinate with stakeholders to ensure that any unavoidable system disruptions and outages are notified well in advance so that affected parties can prepare. Very few foundation works require outages.  Emergency Restoration Team and emergency spares: Maintain readiness of emergency restoration team and structures – ability to temporarily restore a localised failure (up to 5 towers or 2 km) of any one line (double or single circuit) within 10 days where physical Grid redundancy is not available.

These activities and associated strategies are discussed in the following sections. repairs  maintenance projects.FL 01. mostly because there are no moving parts. Preventive maintenance is generally our most regular asset intervention. as little servicing is required. We intend to implement the following two preventive maintenance processes on the foundations fleet in support of our objectives stated in chapter 3. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.4. Condition assessments are very important because of their role in planning replacement and refurbishment to prevent foundation failures. Our approach to Maintenance and the activities it undertakes are described in detail in the Maintenance Lifecycle Strategy. servicing  corrective maintenance . fault response . Page 37 of 58 . The main activities undertaken are listed below.  Servicing: routine tasks performed on the asset to ensure asset condition is maintained at an acceptable level. so it is important in terms of providing feedback of information into the overall asset management system.4 Maintenance We and our service providers carry out ongoing works to maintain assets in an appropriate condition and to ensure that they operate as required. The following discussion focuses on maintenance issues that are specific to the foundations fleet.1 Preventive Maintenance Preventive maintenance is work undertaken on a scheduled basis to ensure the continued safety and integrity of assets and to compile condition information for subsequent analysis and planning.  Inspections: non-intrusive checks to confirm safety and integrity of assets. including specific maintenance projects planned for RCP2. it is also a potential source of safety incidents and human error. condition assessments . For the foundations fleet.  Condition Assessments: activities performed to monitor asset condition or predict the remaining life of the asset. and identify follow up work. TL Foundations Fleet Strategy TP. Being the most common physical interaction with assets. 4. assess fitness for service. Maintenance tasks are classed into three categories:  preventive maintenance . the largest component of preventive maintenance is condition assessment.02 Issue 1 October 2013 4. All rights reserved.

conductors and hardware. however this is being replaced with a MAXIMO.SS 02. Page 38 of 58 . This strategy supports the network performance objectives for foundation assets.4. By the end of 2013 all CA data will be on the MAXIMO system. Foundation condition assessments Carry out regular foundation condition assessments. 4. All rights reserved. New foundation assets are first assessed just prior to expiration of the defects liability period. high-quality data is collected to inform asset planning and decision making.3. 5%–10% of individual towers and pole structures are on partial (half cycle) assessments. As discussed in 2. When significant defects are identified a maintenance job is raised to rectify the issue. We will continue to develop and refine the existing condition assessment process to ensure relevant. make it safe or secure. which is expected to provide clearer reporting of data and trends. scouring and subsidence  third party excavation or construction around tower foundations. the assessment frequency is reduced to 4 years. If the condition assessment score is less than 50. The frequency of patrols will be assessed based on site or corridor safety criticality. condition assessments are carried out on a cyclic basis and entail a detailed inspection of the structure and span.based asset management information system. foundations. Condition assessment is carried out in line with TP.2 Corrective Maintenance Corrective maintenance includes unforeseen activities to restore an asset to service. A ground- based patrol visits each structure foundation to identify any defects that could pose a risk to the structure integrity. and enables planning to take into account the impact of varying environmental ageing factors. even if this is scheduled some time after the initial need for action is identified.17B Transmission line condition assessment Part B: Structures. nationally consistent.FL 01. The programme provides a basis upon which replacement or maintenance options can be investigated. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. TL Foundations Fleet Strategy TP. Sites with unusually rapid degradation or those with higher criticality may be assessed more frequently. The assessment produces a condition assessment score for various components and a defect list. prevent imminent failure and address defects. tower line assets are generally assessed every 8 years.2. At June 2013. It includes the required follow- up action. Thereafter.02 Issue 1 October 2013 Perform regular patrols Carry out regular patrols to allow the planning of work required to mitigate or avoid any failure risks. All CA data is currently stored in our maintenance management system MMS. The condition assessment (CA) programme monitors and records the condition of transmission line structures. Line patrols are generally performed once a year on every transmission line asset. It also allows extrapolation of the assessed condition into the future. Such defects include:  severely damaged foundations  geotechnical risks due to slips.

Activities include:  Fault restoration: unscheduled work in response to repair a fault in equipment that has safety. Page 39 of 58 . it is critical that this be established as quickly as possible. Corrective works may be urgent and if not completed for a prolonged period. Repairs include the correction of defects identified during preventive maintenance and other additional predictive works driven by known model type issues and investigations. a Maintenance Project will be instigated to undertake the repairs works. This supports our network performance and safety objectives.FL 01. 9 Where the number of potential repairs is deemed sufficiently high. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. See the strategy Maintain Contingency Response Resources for details on how we will manage the response of contractors to faults.02 Issue 1 October 2013 These jobs are identified as a result of a fault or in the course of preventive work such as inspections. including urgent dispatch to collect more information  Repairs: unforeseen tasks necessary to repair damage. improve redundancy and remove system constraints by maximising the availability of assets. When the cause is determined. TL Foundations Fleet Strategy TP. All rights reserved. In both cases the repairs are carried out to support the safety and network performance objectives. Repairs We may repair foundations where a fault has been identified that could potentially result in a failure or when a failure has occurred. The purpose of a fault patrol is to establish if the circuit can be safely re-energised and determine the cause of the fault. prevent failure or rapid degradation of equipment  Reactive inspections: patrols or inspections used to check for public safety risks or conditions not directly related to the fault in the event of failure Fault Response Fault response is required to restore the function of assets as quickly as possible to maintain supply to customers.9 Timely repairs reduce the risk of failure. Slope stability and waterway protection works and minor repairs Complete slope stability and waterway protection works and minor foundation repairs at structures where specific defects need repair. repairs are planned and implemented commensurate with the safety risk and asset criticality. reduced network reliability may result. Corrective maintenance has historically been categorised as repairs and fault (response) activities. environmental or operational implications. For the purposes of system performance and safety. Respond to foundation failures in a timely manner Ensure Lines Maintenance contractors have staff patrolling the asset within one hour of being notified of a fault and can respond to two faults at the same time.

The drivers for maintenance projects include asset condition.2. mitigating safety and environmental risks. All are subject to corrosion. All rights reserved.FL 01.3).  Baseplate /anchor bolt: Poor-quality dry-pack mortar originally used under baseplate. The purpose of this strategy is to ensure the integrity of the foundation system is maintained and lifecycle costs are minimised. their refurbishment is considered a maintenance project activity. Moisture ingress under the baseplate has subsequently led to corrosion of the anchor bolts and baseplate (which is not visible until the grout is removed during refurbishment). maintenance projects typically consist of relatively high- value planned repairs or replacements of components of larger assets. The typical threshold score of 50 before any significant rusting or loss of section is visible. their failure has the potential to result in a structure collapse with significant implications for safety and reliability. as such. Some 1. anchor bolts and cast-in stubs at a condition assessment score of 50 prior to onset of significant rusting.5. We periodically review refurbishment criteria and designs to ensure appropriate practice is being employed.3 Maintenance Projects As discussed in subsection 2. Maintenance jobs are typically run as a project where there are operational and financial efficiencies from doing so. but they typically do not extend far into the concrete (<20mm).type foundations is porous and has led to mortar crumbling. Maintenance projects would not be expected to increase the original design life of the larger assets. TL Foundations Fleet Strategy TP. Connection component refurbishments Refurbish corroding baseplates. 4.  Cast-in in-situ stub leg: There are often rust issues at the concrete interface (ringbark corrosion). those with baseplates and anchor bolts and those with cast in stubs. Refurbishment selection is based on the minimum condition assessment score of the four leg-based scores collected at each site. Foundation connection components comprise two types. Regardless.02 Issue 1 October 2013 Works covered by this strategy include:  river diversion or bed protection works  checking/repairing splice and anchor bolts  baseplate/ground connection maintenance and repair where scope is sufficiently small that a maintenance project is not raised  re-forming ground where water pooling around tower bases  works associated rectifying ground subsidence or movement  rectifying damage caused by vehicle or farm activity. Foundation components are considered a relatively minor part of the overall foundation and tower structure and. In extreme TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.2.4. Refurbishment by blasting and painting has proven highly successful. and to improve performance. Over the RCP2 period we intend to implement the following maintenance projects on the foundations fleet.300 baseplate connections currently have a condition assessment score less than 50 (see subsection 2. Page 40 of 58 .

02 Issue 1 October 2013 cases a small area of concrete is broken out. We have 8 towers in a marine environment on the Tiwai causeway supporting the 2 transmission lines that supply Tiwai point. The cost of these refurbishments is derived in line with our volumetric forecasting methodology. Marine foundation refurbishment Refurbish specific foundations in marine environments. property or the Grid. During RCP2. Some 670 stub connections currently have a condition assessment score less than 50 (see subsection 2. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. The typical threshold is condition assessment 50 before any significant rusting or loss of section is visible. This work has an estimated cost of $600. The total expenditure for this strategy is $1.000 – an average of $75. The work is planned for 38 sites on three South Island assets: AHA-OTI-A. discussed in subsection 4.3m over RCP2.1. Transmission line tower foundations are occasionally located in marine environments. which equates to an annual average expenditure of $200.300 for cast-in in-situ leg refurbishments. these connections will require periodic paint maintenance at a repeat cycle of between 12 and 20 years depending on the site environment. The estimated cost of this work is $700.000. we will also complete the marine foundation refurbishment works on the HEN- OTA-A line that began in RCP1. DOB-TEE-A and BLN-KIK-A. this equates to an annual expenditure of $3.0m. Average out-turn costs for baseplate and anchor bolt refurbishments are $7. the steel cleaned.FL 01. We plan to complete the programme of refurbishing existing foundations at sites where failure would pose significant risk to people. Waterway protection works Complete waterway protection work on defective pole foundations in riverbeds. and the area repaired by grouting.900. Page 41 of 58 . TL Foundations Fleet Strategy TP.000 for each tower.4. All rights reserved. Refurbishment selection is based on the minimum condition assessment score of the four leg-based codes collected at each site.3). We plan to complete river protection work on existing pole foundations where river erosion poses a significant threat to security of supply on the Grid. and are $2.5m.000.2. Once refurbished. This is based on existing condition assessment information and expected degradation. We plan to carry out an ongoing connection refurbishment programme of approximately 630 sites each year throughout RCP2 – 360 baseplates and 270 cast-in in-situ legs. Foundation works are planned to protect these foundations from chloride ingress during RCP2. This equates to an annual average expenditure of $260. At 360 and 270 sites respectively. Estimated costs over RCP2 are $1. As a result of this location.000. they are subject to additional degradation from tidal activity and chloride ingress attacking the reinforcing steel.

2 Divestment Implementation of divestment is primarily the change of ownership. Page 42 of 58 .6 Capability We require grid assets and equipment to be maintained. This process and its justification are described fully in the Disposal and Divestment Lifecycle Strategy. Work is to be carried out only by individuals TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. including requirements for foundation removal.02 Issue 1 October 2013 4. TL Foundations Fleet Strategy TP. Foundation divestment Divest foundations as part of transmission line divestments to customers. professionalism and safety. All towers will have associated foundations and these will be divested with the tower structure. we will follow appropriate decommissioning process.5.1 Disposal The Disposal Lifecycle eventuates when foundations are no longer needed or when a foundation has degraded to an extent where refurbishing is uneconomic. The total number of assets to be transferred represents 4% of the total tower and 9% of the total pole fleet as at June 2013. 4.FL 01. This includes all divestments that we believe have a 50% or greater likelihood of occurring during the timeframe. We are continuing with the transfer of a number of assets at the fringes of the existing Grid to our distribution business customers. we carry out diagnostic inspection and testing to investigate the cause of the failure. although we must also remain cognisant of any safety and environmental issues and technical impacts on the Grid such as a change in constraints and flexibility of Grid operation. Decommissioned site foundations should be re-instated to their former natural forms to allow the land to recover. Foundations may be replaced with new ones. Consistent with environmental objectives. We will monitor rehabilitated areas for a period of time after re-instatement. The approach is set out in detail in the Disposal Lifecycle Strategy. 4. tested and operated to high standards of skill. All rights reserved. This subsection describes our approach to the disposal of assets within the foundations fleet.5 Disposal and Divestment The disposal and divestment phase includes the process from when planning of disposal of an asset begins through to when the asset is no longer owned by us. yet there are important requirements for the disposal phase. 4. Site reinstatement Reinstate decommissioned site foundations to their former natural forms. This information is fed into the management of the entire foundation asset fleet. recovery and recycling/disposal of materials. Refer to the Towers and Poles Fleet Strategy for the number of towers and poles likely to be transferred to customers between 2013/14 and 2019/20.5. In the case of a failure.

Ensure the modelling includes lessons learned from the refurbishment programme in relation to observed degradation in various soil types. Page 43 of 58 . All rights reserved. some fields are currently incomplete. Comprehensive records that cover the original installation of a foundation structure and any subsequent modifications are vital to enable quality asset management decisions.6. moisture contents. This helps to prevent injury to workers and damage to assets. Maintain and develop fleet strategies Maintain and develop the fleet strategy for the foundation fleet. Revise building blocks on an ongoing basis using costs from completed works and forecast innovations and improvements. While good asset attribute and condition data is available for most foundation sites. Use these costs in the economic modelling along with degradation rates and AHI to define least lifecycle cost options for programmes of work. type test reports. Maintain up-to-date asset records Maintain up-to-date records of all foundation asset attributes. Data must include details of exactly what is installed.02 Issue 1 October 2013 with competencies that are both appropriate and current (see TP. Continue the development and refinement of models to predict the asset health of foundations. We plan to enhance the failure and incidence records system to improve consistency and usefulness of the data. particularly for grillages. and to protect the public and their property from harm. To improve condition assessment consistency. and TP. The capability strategies are described under three headings:  Asset Knowledge  Risk Management  Training and Competence.25 Minimum Requirements for Transpower field Work). design reports. This section describes the approach used to ensure that these competencies are present in those undertaking work on the foundation and access assets. land use etc.SS 06. Quality condition data is also required. The current project to transition to the MAXIMO-based asset management information system will include a review and cleansing of data. 4.FL 01. condition and performance. Data quality and completeness will continually be reviewed and amended as required to ensure a high-quality dataset is maintained. TL Foundations Fleet Strategy TP.1 Asset Knowledge Robust asset knowledge is critical to good decision making for asset management.SS 06. condition data and investigation reports. improved guidelines will be developed including more photographic examples where relevant.20 Minimum Competencies for Line Maintenance. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. including root cause analysis.

3 Training and Competence We have two service specifications that define the competency requirements for working on transmission line assets. Risk management processes will be made more robust and systematic. TP. we apply an adaptive condition assessment approach where the frequency and extent of condition assessment interventions is determined based on the most recent condition assessment and the predicted current state.SS 06. In recognition of this.25 (Minimum requirements for Transpower field work).3.SS 06. Risk-based options evaluation framework Develop a risk-based framework and associated tools for evaluating foundation investments. Understanding and modelling uncertainty then becomes an increasingly important element in risk management decision making. We maintain a minimum baseline of retained skilled workforce: engineers and site works operators who understand the physical assets. Knowledge of foundation condition is crucial to the assessment of options for foundation replacement and refurbishment. As outlined in subsection 2.20 Minimum competencies for lines maintenance  TP. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.20 (Minimum competencies for lines maintenance) and TP.6.SS 06.SS 06. The risk model will specifically consider uncertainty in the inputs to risk-based decision making.FL 01.6. including foundations:  TP. particularly given the consequences of foundation failure on transmission line performance. We will ensure more robust and detailed development of scope for major replacements to improve the accuracy of cost estimates and the validity of the economic analysis of options. Page 44 of 58 . TL Foundations Fleet Strategy TP. we are developing asset health and criticality frameworks to improve and integrate our risk-based asset management. We will develop an improved risk management framework and tools that can be used across the foundations fleet to evaluate investment options.25 Minimum requirements for Transpower field work. All workers must hold appropriate competencies to work on our assets in line with the service specifications.2. All rights reserved. The key parts of this framework will be tools for making quantitative estimates of the likely impacts of foundation failures on service performance and safety on a span-by-span basis. The strategies below discuss how we plan to progress this in regards to the foundations fleet.02 Issue 1 October 2013 4.2 Risk Management Our approach to risk management is central to our decision making as we seek to achieve our overall asset management objectives and optimise the timing of major investments. and will allow risk assessments to be more readily communicated to internal and external stakeholders. Foundation worker competencies Adhere to the following service specifications. 4.

Page 45 of 58 . Planning Enhancement and Modify existing foundations. Procurement Award contractor work by geographic locations on a sole source ‘yours to lose’ basis. Delivery Planning Package works into blocks of consecutive structures and ensure multiple works are carried out at one site simultaneously wherever possible. refurbish.02 Issue 1 October 2013 Since 2011. asset criticality and other factors. labour and material constraints. Development Use concrete encasement designs as the preferred refurbishment option wherever they can be installed in a cost effective manner. Replacement and Strengthen undersized foundations in all critical locations to minimise the risk of tower failure due to overloading. Integrated Ensure any work that changes loadings on structures includes a robust design assessment of the Works Planning foundation strength to ensure compliance with current standards. Prioritise the refurbishment and strengthening of foundations taking into account existing condition. All rights reserved. Asset management competency Increase and then maintain the in-house skill base with regard to Asset Management. Design replacement foundations to carry the anticipated design loads of likely future upgrades. This has resulted in a considerable increase in service provider training. TL Foundations Fleet Strategy TP. including strengthening and relocation. Cost Estimation Ensure foundation project estimates are developed and scoped to achieve P50 cost value. preferably by concrete encasement.7 Summary of RCP2 Fleet Strategies Our asset management plans for the fleet of foundation assets for each lifecycle stage are summarised in the table below. To ensure better long-term asset management outcomes. Replace access corridor bridges based on condition. all grillages that currently have a condition assessment score less than 30.FL 01. Operations Outage Planning Plan to minimise disruption to customers for foundation works that require outages. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. we plan to increase the emphasis on training in Asset Management principles and application across all relevant parts of the business. skilled manpower and emergency spares in place to enable rapid restoration of transmission service following single or multiple structure failure(s) or conductor Planning drop(s). We plan to continue with this training strategy. to support new structures or to enable upgrading of conductors. Contingency Have sufficient plans. Ensure planned projects are deliverable within available financial. Ensure no grillage foundation has a condition assessment score less than 40 by 2033 (in 20 years). Delivery Ensure assets with high safety or Grid criticality are designed and maintained to be more reliable Design than less critical assets. Refurbishment Replace or refurbish pile foundations based on condition. much of the training has been provided to service providers at no cost (other than the employee’s time). By the end of the RCP2 period. 4. P50 is an estimate of the project cost based on a 50% probability that the cost will not be exceeded.

anchor bolts and cast-in stubs at a condition assessment score of 50 prior to onset of significant rusting. Refurbish corroding baseplates. Management Adhere to the following service specifications.FL 01. Maintenance Complete slope stability and waterway protection works and minor foundation repairs at structures where specific defects need repair. Complete waterway protection work on defective pole foundations in riverbeds. Maintenance Carry out regular foundation condition assessments. TP. condition and performance. Maintenance Projects Refurbish specific foundations in marine environments. Ensure Lines Maintenance contractors have staff patrolling the asset within one hour of being Corrective notified of a fault and can respond to two faults at the same time. Page 46 of 58 . TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. Competence Increase and then maintain the in-house skill base with regard to Asset Management.25 (Minimum requirements for Transpower field work). Risk Develop a risk-based framework and associated tools for evaluating foundation investments. Divestment Divest foundations as part of transmission line divestments to customers. Knowledge Maintain and develop the fleet strategy for the foundation fleet.20 (Minimum competencies for lines Training and maintenance) and TP. All rights reserved. TL Foundations Fleet Strategy TP.02 Issue 1 October 2013 Maintenance Carry out regular patrols to allow the planning of work required to mitigate or avoid any failure Preventive risks.SS 06. Capability Asset Maintain up-to-date records of all foundation asset attributes. Disposal and Divestment Disposal Reinstate decommissioned site foundations to their former natural forms.SS 06.

All rights reserved.FL 01. . TL Foundations Fleet Strategy TP.02 Issue 1 October 2013 Appendices TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.

 The grillage condition score represents the worst of the steel found from 300mm below the ground line to the base of the grillage. Ground line interface Grillage Figure 13: Cross section of a grillage foundation  The picture above shows a grillage foundation and the areas we assess to determine the condition score (condition assessment score). (CA code).  The grillage condition assessment degrades from a score of 100 to 0. TL Foundations Fleet Strategy TP.FL 01. Appendices | page 48 . and a score of 20 means there has been 10% loss of metal cross section and replacement is required.02 Issue 1 October 2013 A GRILLAGE EXAMPLES Figure 13 shows a cross section of a grillage foundation. where a score of 40 means the galvanising is gone and rust is beginning to pit the steel. All rights reserved. The ground-line interface condition represents the worst of the steel found from 100mm above the ground line to 300mm below the ground line. Figure 14 shows grillages at a condition assessment score of 20. Figure 14: Grillages at a condition assessment score of 20 TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.

Figure 15: Grillages at a condition assessment score of 40 TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.02 Issue 1 October 2013 Figure 15 shows grillages at a condition assessment score of 40.FL 01. Appendices | page 49 . TL Foundations Fleet Strategy TP. All rights reserved.

30 Flaking rust. Condition Guidelines Assessment 100 New steel grillage fully galvanised. 20 (Replacement Metal loss on main and/or bracing steel reaches replacement criteria (10% loss of criteria R/C) cross section). Table 5: Grillage Foundation Connection (Buried Grillage – soil/main leg interface) Condition Assessment Guidelines TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. 80 Older grillage (now fitted with cathodic protection (C/P)) otherwise in condition score of 50-60. now visible at the surface. heavy flaking rust. Table 4: Grillage Foundation Condition Assessment Guidelines Condition Guidelines Assessment New (or refurbished steel members. Patches of galvanising gone. 80 New galvanised steel leg without added protective coating. Appendices | page 50 . foundation failure probable under ‘everyday conditions’. 50 Steel rust stained at ground level and just below the surface. C/P no longer effective and foundation deteriorating. TL Foundations Fleet Strategy TP. and some loss of cross section. 90 Surface is dulled to a light grey colouring. pitting and nodules of rust appearing on steel surfaces at ground line and 40 below. 40 Rust beginning to pit steel below ground line (GL) advancing up main leg member. All rights reserved. Complete breakdown of nuts and bolt heads. 10 Metal loss exceeds replacement criteria. 70 Protective coating failing. 0 Serious risk of tower leg tension/compression failure. 10 Rusting exceeds R/C. Severe rusting of steel about ground line and below. 30 Flaking rust on main leg section of grillage just below GL.02 Issue 1 October 2013 B FOUNDATION CONDITION CODES Table 4 shows the grillage foundation condition assessment guidelines.FL 01. 60 Start of steel member surface rusting. but tower not significantly at risk. 0 Metal loss serious. but tower not significantly at risk. correctly backfilled and compacted as is standard. 50 Steel surfaces below ground beginning to develop rust spotting. Table 5 shows grillage foundation connection (buried grillage – soil/main leg interface) condition assessment guidelines. 60 Speckled rust. 70 Bolts beginning to rust beneath the surface. with added protective 100 coating in as-new condition). 90 Protective coating 50% of way to failure. Loss of metal. galvanised and free of damage. black underneath 20 (R/C) with loss of metal cross-sectional area of approximately 10%.

60 Embedded reinforcing cage rusting. 70 Protective paint depleted. minor rust. 80 Reinforcing exposed to soil severely corroded. Minor spalling to 20 (R/C) concrete as rust penetrates beneath the concrete surface. TL Foundations Fleet Strategy TP. with associated underground cracking/spalling. 10 Metal loss exceeds 20%. 50 Loss of galvanising from interface/leg surface.FL 01. 70 Exposed reinforcing. Condition Guidelines Assessment 100 New foundation. and no longer able to reliably sustain ultimate site- 20 (R/C) specific design loads with reliability. 30 Main reinforcing seriously corroded. but less than 40%. Galvanising on leg dulled. without obvious deterioration. Foundation severely cracked unable to sustain design loads. 30 5% metal loss on leg /concrete interface surface. Table 7: Foundation Connection (cast-in-situ steel stubs/concrete interface) Condition Assessment Guidelines TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. 40 Main vertical reinforcing start corroding. major spalling off the cap. but no visible deterioration. Minor spalling off the cap. 40 Rust pitting at concrete/steel interface. Flaking rust and loss of metal cross section of 10% at concrete level. increased rust staining. causing serious spalling/cracking etc. Expansion cracks in cap. 0 Metal loss exceeds 40%. concrete darkening and surface roughening. 60 Specks of rust appearing at concrete steel interface. Table 7 shows the foundation connection (cast-in in-situ steel stubs/concrete interface) condition assessment guidelines. Table 6: Concrete Foundation Condition Assessment Guidelines Condition Guidelines Assessment New foundation. 50 Spiral reinforcing in some areas corroding. All rights reserved. due to crumbling of concrete mass and/or corrosion of the reinforcing.02 Issue 1 October 2013 Table 6 shows the concrete foundation condition assessment guidelines. heavy staining around leg. is protectively painted 300mm 100 either side of concrete surface level. Protective paint at 80 concrete level showing signs of peeling or wear. Galvanised leg section is free of damage. 90 Foundation in service at least 10 years. but not at immediate risk of 10 failure. Appendices | page 51 . Foundation at replacement criteria. in good condition. 0 Uplift failure possible under ‘everyday conditions’. 90 At least 5 years of service.

Rust staining appearing as a brown/red rim on bottom of baseplate. baseplate surface rust. 90 Surface coating deteriorating. 20% metal loss on any one bolt and 10% metal loss over all anchor bolts. New surface protective coating to seal out any water. or serious risk to tower at a less 0 loss level where structure heavily loaded. but still effective. bolts corroding. Metal loss on anchor bolts which prevents the withstanding of ultimate site-specific design 10 loads. Rusting of bolt threads and 30 nuts below the baseplate. First speckled rust 50 appearing on anchor bolt threads. Condition Guidelines Assessment New or refurbished galvanised steel baseplate onto concrete held anchor bolts. Significant rusting to bottom of baseplate. but no loss of steel. 60 First sign of rust staining at edge of baseplate. Flaking rust to bottom of baseplate. Waterproof 100 mortar packed tightly between baseplate and concrete foundation. Chunks of mortar gone exposing significant rusting of 20 (R/C) inner bolts and baseplate /levelling nuts. Table 8: Foundation Connection (anchor bolts and baseplate /mortar and concrete Interface) condition assessment Guidelines TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. TL Foundations Fleet Strategy TP. mortar in good condition. 50% or more loss of cross section on anchor bolts overall.FL 01. 40 Mortar crumbling. and critical areas discoloured. All rights reserved.02 Issue 1 October 2013 Table 8 shows the foundation connection (anchor bolts and baseplate/mortar and concrete interface) condition assessment guidelines. 80 Protective coating ineffective. Appendices | page 52 . 70 Baseplate and anchor bolt galvanising rough.

500 3.FL 01. GRILLAGES AT OR BELOW CA 40 (300/YEAR) CA 31-40 CA 0-30 3.500 1.  Plan fails to meet the objectives stated in section 4.000 1. The following two sections show the impact of refurbishing 300 and 200 tower grillages each year.02 Issue 1 October 2013 C GRILLAGE ENCASEMENT MODELLING As discussed in sections 2.1.2.1.2. Appendices | page 53 . TL Foundations Fleet Strategy TP.1.2.500 2. to the most recent ground-line condition recording. no grillages with CA less than 30 by 2020. that is. but where it is prudent to refurbish them at the same time as the others to minimise landowner disruption).  Prioritisation as shown in the matrix in Figure 8.2 shows the impact on condition if the proposed plan to refurbish 350 of the worst condition tower grillages each year is followed (plus an additional 50 each year which are not in such poor condition. It assumes a linear degradation rate from the original installation date (at condition assessment 100). Figure 16 shows the effect of the encasement plan on grillage condition.000 500 0 Jun-2013 13/14 14/15 15/16 16/17 17/18 18/19 19/20 Figure 16: At-Risk Grillage Forecast (300 encasements/year) TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. then continues linearly to forecast future condition.000 2. a model has been created to predict current and future grillage condition and asset health.4 and 4. All rights reserved. Subsection 4. Encase 300/Year Key points of alternative plan 300/Year:  Target 300 grillage encasements each year.

500 1. that is.000 2. GRILLAGES AT OR BELOW CA 40 (200/YEAR) CA 31-40 CA 0-30 3.FL 01.ASSET HEALTH (19/20 .300/YEAR) 12+ YRS (88%) 7-12 YRS (5%) 2-7 YRS (4%) 0-2 YRS (2%) NOW DUE (1%) Figure 17: Foundation Asset Health Forecast (300 encasements/year) Encase 200/Year Key points of alternative plan 200/Year:  Target 200 grillage encasements each year.2.  Plan fails to meet the objectives stated in section 4.1. no grillages with CA less than 30 by 2020 Figure 18 shows the effect of the encasement plan on grillage condition.02 Issue 1 October 2013 Figure 17 shows the effect of the programme on foundation asset health/remaining life at the end of RCP2. FOUNDATIONS .500 2.000 1. Appendices | page 54 .  Prioritisation as shown in the matrix in Figure 8.500 3. All rights reserved. TL Foundations Fleet Strategy TP.000 500 0 Jun-2013 13/14 14/15 15/16 16/17 17/18 18/19 19/20 Figure 18: ‘At-Risk’ Grillage Forecast (200 encasements/year) TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.

02 Issue 1 October 2013 Figure 19 shows the effect of the programme on foundation asset health/remaining life at the end of RCP2. FOUNDATIONS .FL 01. All rights reserved.ASSET HEALTH (19/20 . Appendices | page 55 . TL Foundations Fleet Strategy TP.200/YEAR) 12+ YRS (85%) 7-12 YRS (5%) 2-7 YRS (4%) 0-2 YRS (2%) NOW DUE (4%) Figure 19: Foundation Asset Health Forecast (200 encasements/year) TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.