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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

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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

The strategy is to refurbish. The plan involves investigating foundations at 40 towers each year and strengthening 8 each year over RCP2. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. all grillages that currently have a condition assessment of less than 30 by 2020. All rights reserved. The strategy is to strengthen undersized foundations in all critical locations to minimise the risk of tower failure due to overloading. 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). The plans will involve refurbishing approximately 400 grillages each year at an annual cost of $10. Page 3 of 58 . Capital Expenditure Grillage Refurbishments RCP2 Cost $51m A large number of grillages are deteriorating due to their age and environment. and ensure no grillage foundation has a condition assessment of less than 40 by 2033 (in 20 years). generally by concrete encasement. Well maintained access tracks are essential to allow safe access to transmission line assets when responding to faults or performing routine inspections and maintenance. The plan involves 64 bridge replacements over RCP2. 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. tower structure collapses and conductor drops. 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.4m Poor design process used for foundations constructed before 1983 has led to the occasional installation of undersized bored concrete foundations. Undersized Foundation Strengthening RCP2 Cost $4. TL Foundations Fleet Strategy TP. Grillage refurbishments extend the life of grillages and reduce the chance of foundation failure. Bridge Replacements RCP2 Cost $6.FL 01.2m. Strengthening undersized foundations reduces the chance of tower structure collapse (with significant implications for safety and reliability).1m A number of bridge replacements are required on access corridors to maintain access to the transmission lines and structure foundations.

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

TL Foundations Fleet Strategy TP.1 Purpose We plan. 1. and the Environmental Protection Authority  Department of Conservation  service providers  customers. Operations. 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. including distribution network businesses and generators. local and regional Councils. These activities include Planning. Delivery. Electricity Authority.FL 01. All rights reserved.2 Scope The scope of the strategy includes the foundations of towers and non-direct buried poles. 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. 1.02 Issue 1 October 2013 1 INTRODUCTION Chapter 1 introduces the purpose. stakeholders. build. Page 5 of 58 .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. The strategy sets the high-level direction for fleet asset management activities across the lifecycle of the fleet. This document has been developed based on good practice guidance from internationally recognised sources. scope. and Maintenance. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. Performance and Projects)  regulatory bodies: Commerce Commission. Key stakeholders include:  landowners  relevant Transpower Groups (Grid Development. 1. including BSI PAS 55:2008. This includes objectives for future performance and strategies being adopted to achieve these objectives. and strategic alignment of the foundations fleet strategy. maintain and operate New Zealand’s high-voltage electricity transmission network (‘Grid’) including the foundations that support conductor-bearing structures (towers and poles).

The strategy directly informs the portfolio asset management plans. TL Foundations Fleet Strategy TP. These objectives have been aligned with the corporate and asset management policies. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.5 Document Structure The rest of this document is structured as follows. 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. It indicates where this fleet strategy and plan fit within the asset management system. This hierarchical connectivity is represented graphically in Figure 1. Chapter 3 sets out asset management related objectives for the assets. Chapter 4 sets out the fleet specific strategies for managing the assets.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. Appendices are included that provide further detailed information to supplement the fleet strategy. characteristics and their performance. 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. and higher-level asset management objectives and targets.02 Issue 1 October 2013 1. All rights reserved.FL 01. Chapter 2 provides an overview of transmission line foundations including fleet statistics. Page 6 of 58 . and the daily activities of managing the assets.

It is important to maintain these in an appropriate condition through timely maintenance and refurbishment. asset condition. soil type and the preferred construction practices of the day. asset health.000 route km of transmission line.FL 01.02 Issue 1 October 2013 2 ASSET FLEET Chapter 2 describes the asset fleet with a focus on:  asset statistics – including population. 2.1 Asset Statistics This section outlines the foundations asset fleet population. there are approximately 25. 2. As at 30 June 2012. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.1 Asset Population The Grid is made up of approximately 12. The quantities of each type (along with descriptions) are shown in Table 1. Foundations vary in size and type depending on the design loads. Page 7 of 58 . and spares  asset characteristics – including safety and environmental considerations. Foundations play an important role on the Grid by supporting transmission line towers and poles. 2. This results in an increased risk of foundation and subsequent tower failure.000 transmission line support structures (such as towers and direct buried poles). safety and environmental and identification of risks and issues. age profile. diversity. supported by approximately 41. All rights reserved.2 Fleet Diversity Asset fleet diversity is an important asset management consideration. which in turn support conductors. maintenance requirements and interaction with other assets  asset performance – including reliability.000 foundation-supported structures on the network (such as towers). asset criticality. More than half of all tower foundations are original buried steel grillage foundations that are subject to corrosion. TL Foundations Fleet Strategy TP.1.1. along with the diversity and age profiles of the physical assets.

TL Foundations Fleet Strategy TP. Buried steel grillage foundations are the oldest type of tower foundation on the Grid and comprise more than half of all tower foundations. Page 8 of 58 . Since then.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. Over 600 grillage foundations were refurbished by re-galvanising between 1992 and 2008 and are treated as being new from that date. 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.500 towers have baseplate and anchor bolt connections. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.FL 01. All rights reserved. FOUNDATIONS. essentially all foundations have been constructed with a concrete pile/plug and cast-in stub leg.1.02 Issue 1 October 2013 Foundation Type Description Population Towers Steel Grillage Grillages that have not yet been refurbished 12.350 Concrete over Steel Grillage Refurbished grillage foundations (by encasement in concrete) 1. Of the concrete foundations. Figure 2 depicts the diversity of the asset fleet.913 Table 1: Foundation Types and Populations as at 30 June 2013 The type of foundation used has varied with time.DIVERSITY GRILLAGE (50%) CONCRETE OVER GRILLAGE (7%) CONCRETE PLUG. yet the bulk of the population are aged between 45 and 90. They were the preferred foundation type until the late 1960s when concrete foundations were introduced. some 6.3 Age Profile Foundation assets have been installed progressively since the 1930s. The proportion of concrete foundations will increase over time as new lines are constructed.667 Concrete Plug (bored dug) Currently preferred foundation type 9. lines are divested or decommissioned and grillages are encased with concrete. This type of foundation and connection was installed between the mid-1960s and the late 1970s. BORED OR DUG (40%) OTHER TOWER FOUNDATIONS (3%) POLE FOUNDATION (1%) Figure 2: Foundations – Diversity 2.

This achieves. It is based on observed life and typical condition degradation rates for each foundation type. an expected 120-year life extension with correct maintenance in place.Other 27 50 Timber or steel piles driven into riverbeds foundations Table 2: Foundation Life Expectancy TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.2. 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. FOUNDATIONS .AGE PROFILE GRILLAGE CONCRETE OVER GRILLAGE CONCRETE PLUG. Page 9 of 58 . BORED OR DUG OTHER POLE FOUNDATION 1.02 Issue 1 October 2013 The age profile of the foundation fleet is shown in Figure 3. The actual life will depend on the specific site.000 500 0 0 10 20 30 40 50 60 70 ≥80 AGE (YEARS) Figure 3: Foundations .500 1. Life expectancy should be interpreted as the period after which the risk of failure is deemed unacceptable. on average.3). One of the fleet’s main strategies relates to the effective replacement of grillage foundations through concrete encasement.Age Profile Foundation life expectancy The life expectancy for each type of foundation is shown in Table 2. works are always planned based on actual condition. not age (see subsection 2. TL Foundations Fleet Strategy TP. and construction quality. 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 . All rights reserved.FL 01. While age is of interest for predicting future needs. weather exposure.

A framework has been developed for transmission line assets. 2.2 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.2.2. All rights reserved. The risk is clearly dependant on land use. fire and physical impact damage. particularly when working in sensitive areas such as riverbeds. the level of reliability required by the customers.1 Safety and Environmental Considerations We are committed to ensuring that safety and environmental risks are minimised at all times. 2. These characteristics and the associated risks are discussed in the following subsections. Highly critical assets will be designed and maintained to provide a higher level of reliability than less critical assets. Prevention of tower failure Foundation failure leading to a tower failure and conductor drop is a significant safety consideration with risk of electrocution. The most significant safety and environmental consideration for the foundations asset fleet is the prevention of a transmission structure failure.2 Asset Criticality Our approach to asset management has been adapted to recognise the differing levels of asset criticality.02 Issue 1 October 2013 2. Page 10 of 58 . and is higher in urban environments and over busy roads than in back country rural environments.FL 01. and the level of redundancy. TL Foundations Fleet Strategy TP. The methodology considers various aspects that would be impacted by a failure such as load carried. 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). Regular condition assessments and a robust design process are essential to minimise the risk of foundation failures. constraints that would be placed on the rest of the Grid. Environmental There is potential for significant environmental impacts when constructing or removing foundations. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. Further information on the asset criticality approach is provided in the document ‘Asset Risk Management – Criticality Framework’.

no reliable non-intrusive method has been found to accurately predict which towers have corroded grillages. Age.4 and 4. Subsections 2. A separate condition assessment score is recorded for each. 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. Excavation and inspection (see Figure 5) is relatively TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. At a condition assessment score of 20. Grillage foundations Many towers with buried steel grillage foundations are now showing corrosion on tower legs and bracing near the ground line. We are still at a relatively early stage in the development and application of safety criticality. the foundation. 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. These assessments produce a condition assessment score. the foundation is incapable of carrying its full design loads. Sites with a high consequence of failure may be assessed more frequently. the assessment period is reduced to 4 years.2. All rights reserved.FL 01. original galvanising quality. New foundation assets are first assessed just prior to the expiration of any defect liability period.02 Issue 1 October 2013 Figure 4 shows the proportion of foundations in each criticality category. soil type and moisture content are all known to influence the grillage condition. Page 11 of 58 . Despite numerous national and international trials. 2. If the condition assessments score is less than 50. in combination with asset health to determine prioritised replacement programmes. TL Foundations Fleet Strategy TP. During regular condition assessments the two locations assessed are: 1. Thereafter. The reliability and performance of these assets need to be managed carefully to minimise failure risks.3 Asset Condition Regular condition assessments on foundations are carried out to assess their condition. and will continue to refine and develop this throughout RCP2. 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. tower line assets are generally assessed every 8 years.1. the foundation connection 2. The only reliable method of determining the condition of the buried part of the foundation condition is to dig and visually inspect.2.2 discuss how criticality is taken into account.

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. in half the cases the grillage was in better condition than the ground interface. Page 12 of 58 . varies from light to severe. Given the high cost and landowner disruption associated with accurately assessing the condition of the buried part of the foundation. Consequently grillage condition assessment has been carried out on a sampling basis. For concrete foundations with bolted connections or cast-in stubs. at the grillage level. TL Foundations Fleet Strategy TP. Less than 1. All rights reserved. Excavations undertaken on some 1. the connection relates to the steel/concrete interface. Of the 7% outside 20 condition assessment points. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.02 Issue 1 October 2013 expensive and also leads to accelerated corrosion.000 towers have had their grillage foundations condition assessed to the base of the grillage.5 to 3m below ground level. Figure 5: Excavated Grillage The bottom of a grillage foundation is typically 2.FL 01. and is within 20 condition assessment points 93% of the time. assessing the steel at this depth is disruptive and expensive. As discussed above. we now use the ground-line interface condition as a proxy for the lower grillage condition. as oxygen will enter into what was a largely oxygen-starved system.000 towers have revealed that the extent of corrosion further underground. Assessment guidelines for foundations are included in Appendix B. For grillage-type foundations the connection is deemed to be the steel from 100mm above ground level to 300mm below.

type foundations is porous and has led to mortar crumbling. Concrete foundations with cast-in stub legs are generally in good condition. the steel cleaned. As for grillages.000 5. Poor quality dry-pack mortar originally used under baseplate. Refurbishment by blasting and painting has proven highly successful.FL 01. BORED OR DUG OTHER 6.CONDITION GRILLAGE CONCRETE OVER GRILLAGE CONCRETE PLUG.000 4. Typically. Page 13 of 58 . the rust does not extend very far into the concrete (<20mm). Foundation connection components For concrete foundations with bolted connections or cast-in stubs. the foundation connection becomes a cast-in stub-type arrangement.000 2.000 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.02 Issue 1 October 2013 FOUNDATIONS . a large number of foundation connection components are deteriorating due to their age and environment. and the area repaired by grouting. 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).000 1. but an increasing number are starting to corrode at the concrete and steel interface. In extreme cases a small area of concrete is broken out. Assessment guidelines for foundations are included in Appendix B. Note that once a grillage foundation is refurbished by concrete encasement.000 3. TL Foundations Fleet Strategy TP. The majority of the fleet has a condition assessment score of above 40 although approximately 1. All rights reserved.400 (or 11%) of grillage foundations are at or below condition assessment 30. the connection relates to the steel/concrete interface. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. 1 Using ground-line condition as a proxy for grillage foundations.

Asset health indicators provide a proxy for the probability of failure in asset risk management analysis.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.4 Asset Health The AHI reflects the forecast remaining life for any given asset – in effect. and so affect the rate of corrosion of steel towers. this is when the foundation can no longer be relied upon to carry its design loads.CONDITION BASEPLATE / ANCHOR BOLT CAST IN SITU STUB LEG 3. Foundation component refurbishment is based on the minimum condition assessment score of the four leg-based codes collected at each site.2. which is used to optimise the level of investment in the fleet. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. such as total replacement of the asset or refurbishment that significantly extends the original design life. Page 14 of 58 .02 Issue 1 October 2013 FOUNDATION COMPONENTS .FL 01. 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. major intervention is required. or is uneconomic). More details on our asset health methodology are set out in the document ‘Asset Risk Management – Asset Health Framework’. Asset health information is used in combination with asset criticality data to assign an overall priority to each asset. The typical threshold is condition assessment 50 before any significant rusting or loss of section is visible. All rights reserved. For transmission line foundations. 2.000 1. 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. TL Foundations Fleet Strategy TP. 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. We are still at a relatively early stage in developing and applying asset health indicators. such as proximity to the coast. it is an assessment of current and future asset ‘fitness for purpose’.000 2. At this point.

which is used to optimise the level of investment in the fleet. the failure risk changes very little. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. TL Foundations Fleet Strategy TP. 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). FOUNDATIONS. Below a score of 30. Page 15 of 58 . ground-line interface condition has been used as a proxy for grillage condition as discussed in subsection 2. Figure 8: shows that prioritisation is based on a combination of condition (remaining life) and criticality.2. due to the heightened risk of them failing. 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. there is a slight increase in the risk of failure. CA 30 has been selected for grillages to account for the uncertainty regarding their below-ground condition. Asset health information is used in combination with asset criticality data to assign an overall priority to each asset. a number of ageing foundations have a relatively poor condition. As the condition assessment score reduces below 20. All rights reserved. the risk of failure increases markedly. A linear degradation rate from the original installation date to the most recent condition assessment score is assumed.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. Between a score of 100 and 30.3 above. While the overall health of the tower foundations is generally good.2 For grillages. the better our understanding in this area will be. 2 Literature on in-ground corrosion of galvanised steel suggests the corrosion rate is roughly linear while galvanising is still there.FL 01. The manner in which asset health is taken into account in the management of the assets is described further in chapter 4. ‘Now Due’ grillages with a condition assessment score under 30 are a higher priority than a high criticality site just reaching 40. As an example. but may actually decrease once corrosion starts. The more replacements we do.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.

to visually identify any defects. we periodically undertake maintenance projects. repairs  Maintenance Projects. condition assessments are carried out on a cyclic basis and entail a detailed inspection of the structure and span.2. Preventive maintenance Line patrols are generally performed once a year on every transmission line asset. Repair jobs are raised in the Maintenance Management System and the maintenance contractors are responsible for carrying out this work. The most common fault response and repair work required for foundations relate to foundation failures due to land subsidence or rapid soil erosion.02 Issue 1 October 2013 2. Detailed maintenance requirements are included in the relevant service specification documents. In addition. Contributing factors include:  severely damaged foundations  geotechnical risks due to slips. condition assessments . The assessment produces a condition assessment score for various components and a defect list.2. The most common types of maintenance carried out on lines assets are:  preventive maintenance. 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. Page 16 of 58 . TL Foundations Fleet Strategy TP. Each year a number of sites require stabilising work and repairs to avoid failure. A ground-based patrol visits each structure/span and walks the conductor line. A patrol report identifies defects required to be rectified. fault response .3. All rights reserved. These requirements have informed the maintenance strategies discussed in section 4. including: . if possible.FL 01. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. scouring and subsidence  third party excavation or construction around tower foundations. servicing  corrective maintenance. The Maintenance Lifecycle Strategy provides further details on our approach to the above maintenance works. which are programmes of works (essentially made up of small projects) used to address repetitive issues identified through preventive maintenance or fault responses. The main purpose of the patrols is to identify defects and sites with very high safety criticality that may then be patrolled more frequently. In extreme cases a structure may be relocated. including: . As discussed in 2.4.5 Maintenance Requirements This subsection describes the maintenance requirements of the foundation fleet.

conductors were transferred to a temporary structure prior to the foundation (and tower) failure. mitigating safety and environmental risks. 2.8m $2.6 Interaction with other Assets The foundations programme is closely aligned with conductor and tower works. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. with established modern design practices the probability of foundation failure is low. the remaining seven were due to high wind events pulling the foundations from the ground. Connection component refurbishments Foundation connection components comprise two types.3. This constitutes a RCP2 strategy and is discussed in more detail in subsection 4. Maintenance projects would not be expected to increase the original design life of the larger assets. land movement and washout do occur.3. Similarly.4. While foundation failures due to extreme climatic loading. 2. In this instance. as any new tower work requires foundation work. Five failures were caused by land movement or river scour. the steel at the concrete interface of cast-in in situ foundation legs is painted prior to significant rusting. These integration processes are managed through the Integrated Works Planning (IWP) processes discussed in subsection 4.3. All are subject to corrosion. Since 1963 there have been 12 foundation failures. Maintenance jobs are typically run as a project where there are operational and financial efficiencies from doing so.9m Table 3: RCP1 Spend on Maintenance Projects 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.02 Issue 1 October 2013 Maintenance projects Maintenance projects typically consist of relatively high-value planned repairs or replacements of components of larger assets. Reliability is measured primarily by the frequency and length of outages.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.1. Future maintenance projects are discussed in subsection 4. and to improve performance. All rights reserved. those with baseplates and anchor bolts and those with cast-in stubs.3. Since 2005. Historic spend – maintenance projects Table 3 provides an overview of historic maintenance project expenditure. Project 2009/10 2010/11 2011/12 Total Various $2. only one tower foundation failure has occurred and was due to river washout.0m $2. TL Foundations Fleet Strategy TP. Examples of past maintenance projects are set out below. 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.1m $6.3 Asset Performance This section describes the historic performance of foundation assets and any associated risks and issues.2. Page 17 of 58 . The drivers for maintenance projects include asset condition.FL 01.4.

ITOMS considers overall transmission line performance (not on an asset type basis.3 Performance Benchmarking International Transmission Operations & Maintenance Study (ITOMS) involves performance comparisons (including reliability) between 27 utilities. Limited effectiveness of near-surface visual inspections Severely rusting foundations on the network present a major risk. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. 3 Details can be found in the Conductors and Insulators fleet strategy. however there is a risk that the condition of any buried grillage is worse than predicted. Recent studies. 2. 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.02 Issue 1 October 2013 In many instances. such as tower foundations). leading to undersized foundations occasionally being installed. including full-scale foundation testing.3 2. property or the Grid.FL 01. A slight conservative approach is therefore warranted.4 Risks and Issues This subsection briefly discusses risks and the identified issues relating to the foundation asset fleet. compounded by the fact that foundations buried at depth cannot be readily condition assessed. condition assessments and line patrols identify foundation issues before towers fail. 2. Structures with concrete pile foundations built before 1983 continue to be investigated. with priority given to sites whose failure would pose significant risk to people. Page 18 of 58 . All rights reserved. Age profiles Grillage foundations are the oldest type of foundation. 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. Some below-ground sampling has been carried out to inform the asset management approach. We maintain a register of problematic areas and at-risk structures are monitored after major weather events.3. This overall performance is considered in the Conductors and Insulators fleet strategy. suggest that under-strength foundations still exist in some cases. as we work closely with authorities and landowners to mitigate any adverse effects associated with our works. Approximately 10% of grillages and foundation components are now corroded to the point of requiring replacement or refurbishment. Age-based deterioration is the major driver of the work programme related to this asset fleet. Our environmental record is considered to be very good.3.2 Safety and Environmental Performance No people have been harmed by any foundation failure on our network. TL Foundations Fleet Strategy TP.3. with the bulk of the fleet now aged between 45 and 90.

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

Grid Performance objectives state that a set of measures are to be met for GXPs based on the criticality of the connected load. 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. In addition Asset Performance objectives linked to system availability have also been defined. these objectives have been aligned with the corporate objectives. No major failure of foundation assets with high or very high safety criticality. All rights reserved. at least lifecycle cost.2 Service Performance Ensuring appropriate levels of network performance is a key underlying objective.FL 01. 3. Safety is a fundamental organisational value and we consider that all incidents are preventable. Less than 1 foundation failure every 5 years. These objectives are set out below. Zero injuries caused by foundation failures. Page 20 of 58 . As described in section 1. 3. . We have specified our network performance in terms of Grid Performance (reliability) and Asset Performance (availability) in our Asset Management Strategy. The current rate is 1. Further objectives in the following areas have been defined:  Safety  Service performance  Cost performance  New Zealand communities  Asset management capability.4. Service Performance Objectives for Foundations . and higher-level asset management objectives and targets as set out in the Asset Management Strategy. Our overarching vision for our foundations fleet is to maintain them in perpetuity.2 every 5 years. TL Foundations Fleet Strategy TP. Safety Objectives for Foundations . and to ensure the integrity and reliability of tower structures and the conductors they support. Recognising the reduced level of control we have in relation to public safety.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. Chapter 4 discusses the strategies to achieve them. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. These high-level objectives are supported by a number of fleet specific objectives.02 Issue 1 October 2013 3 OBJECTIVES Chapter 3 sets out asset management objectives for transmission line foundations. and we will work towards these being formally linked in the future.

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. Improved efficiency through extension of the planning horizon.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.FL 01. Page 21 of 58 . 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. Maintain effective relationship with stakeholders affected by foundation works. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.3 Cost Performance Effective asset management requires optimising lifecycle asset costs while managing risks and maintaining performance. Disestablished site foundations should be re-instated to their former natural forms to allow the land to recover. Design. . . No damage to third party property due to foundation failures. To achieve this. such as erosion and sediment control during site works. TL Foundations Fleet Strategy TP. Minimise cost of works by packaging work into blocks of consecutive structures wherever possible. New Zealand Communities Objectives for Foundations .02 Issue 1 October 2013 3. 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. Minimise stakeholder disruption by packaging work into blocks of consecutive spans wherever possible. we have set out a number of maturity and capability related objectives. . . . . All rights reserved. We are committed to implementing systems and decision- making processes that allow us to effectively manage the full lifecycle costs of our assets. Cost Performance Objectives for Foundations .5 Asset Management Capability We aim to be recognised as a leading asset management company. construct and maintain foundations to minimise lifecycle costs while meeting required levels of performance. Compliance with RMA 1991 requirements. 3. 3. .

We currently use asset criticality and asset health as proxies for a fully modelled asset risk approach. Enhance the failure and incident records system to improve consistency and usefulness of data. 3. Finalise and implement the safety and network criticality categorisation systems for foundation applications. . Page 22 of 58 . . . Formalise and implement an asset management approach that is differentiated by network and safety criticality. Expand knowledge of foundation condition through scheduled condition assessment and analysis of as-found condition during the foundation replacement and refurbishment programme.2 Asset Knowledge We are committed to ensuring that our asset knowledge standards are well defined to ensure good asset management decisions. including experience from assets on our network and condition information. .1 Risk Management Understanding and managing asset-related risk is essential to successful asset management. Continuously improve the asset health modelling of foundations. All rights reserved. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.5. TL Foundations Fleet Strategy TP. Relevant asset knowledge comes from a variety of sources.FL 01. 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).02 Issue 1 October 2013 3. Improve the condition assessment consistency through improved guidelines (such as photographic examples).5. We have commenced this by prioritising fleet replacement expenditure programmes. including root cause analysis. 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. Develop a risk-based model for assessing the trade-offs between different work methods (such as live line techniques). Asset criticality is a key element of many asset management systems. . Asset Knowledge Objectives for Foundations . This asset knowledge must be captured and recorded so that it can be conveniently accessed. Risk Management Objectives for Foundations . based on the criticality framework.

5. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. Page 23 of 58 . Continuous Improvement and Innovation Objective for Foundations . Training and Competency Objectives for Foundations . 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. Increase and then maintain the in-house skill base with regard to asset management principles and application. All rights reserved. . TL Foundations Fleet Strategy TP.5. 3.FL 01.3 Training and Competency We are committed to developing and retaining the right mix of talented. competent and motivated staff to improve our asset management capability.02 Issue 1 October 2013 3. All foundation works to be carried out by service providers that are suitably qualified and competent for the specific tasks required. A large source of continual improvement initiatives will be ongoing learning from our asset management experience.

technology changes and failure TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. The majority of capital expenditure consists of grillage refurbishment. but also include expenditure from 1 July 2013 to the beginning of the RCP2 period and some expenditure after the RCP2 period where relevant. while operating expenditure is mainly covered by section 4.1. The planning lifecycle strategies for these processes are described in the subsections below. The main types of investment considered in this strategy are enhancement and development. TL Foundations Fleet Strategy TP. We support our planning activities through a number of processes. Planning activities Planning activities are primarily concerned with identifying the need to make capital investments in the asset fleet.2. 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. 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. Page 24 of 58 . The strategies are aligned with our lifecycle strategies below and the chapter has been drafted to be read in conjunction with them. training and competence.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. and replacement and refurbishment works. Scope of strategies The strategies focus on expenditure that is planned to occur over the RCP2 period (2015– 2020). Capital expenditure planned for the period is covered by the strategies in section 4. including:  IWP  cost estimation. compliance with Grid reliability standards.1.4. All rights reserved.02 Issue 1 October 2013 4 STRATEGIES Chapter 4 sets out the fleet specific strategies used to manage the foundations asset fleet. which is described in subsection 4. These drivers include demand growth.FL 01.  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. 4.

It does not improve its attributes. and strengthen other foundations as part of specific enhancement projects. 4 For more details. Following completion of the project. Page 25 of 58 . Specific examples that drive capital investment in foundation assets include:  new line developments or uprating of existing circuits.2 Replacement and Refurbishment This subsection describes replacement and refurbishment strategies for the foundations fleet. foundations that do not comply with current design standards are strengthened. As part of uprating projects. which is carried out to ensure that an asset is able to perform its designated function for its normal life expectancy. System growth projects principally include new greenfield lines or the uprating of existing lines. The tower investments are undertaken to meet expected system growth and to ensure appropriate reliability for customers. This is distinct from maintenance work. which may require stronger structures and foundations. We use condition assessment data gathered during refurbishment programmes to model the condition of grillages that have not yet been refurbished. 4. the costs will be allocated out to the relevant foundation asset. Any asset management related costs following their initial installation will be managed through the foundations portfolio. The timing and cost of works will be driven by the relevant conductor works.02 Issue 1 October 2013 risk (indicated by asset criticality and health measures). we will install a number of new tower structures and their associated foundations. which is driven by failure risk. All rights reserved. see the Conductors and Insulators fleet strategy. Refurbishment is expenditure on an asset that creates a material extension to the end of life of the asset. Prioritisation is undertaken on the basis of asset health and asset criticality. enabling better works prioritisation. to support new structures or to enable upgrading of conductors.FL 01. Specific interventions have been defined for foundations based on their condition and informed by their relative criticality.4 4. TL Foundations Fleet Strategy TP.1 Enhancement and Development The most important driver for new foundation investments is the facilitation of new or strengthened towers. In the next few years. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. the cost for such foundation work is currently included in the relevant conductor projects. Facilitate line projects Modify existing foundations. where the priority is higher for assets where the consequence of failure is higher. Replacement is expenditure to replace substantially all of an asset. From a planning perspective.1. which is driven by demand  condition of grillages and other foundation components  foundation strengthening and replacements. These projects drive the need to invest in foundations.1. Condition driven projects Foundation replacement and refurbishment works are primarily triggered by asset condition represented by condition assessment score. including strengthening and relocation. to increase reliability.

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

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

Foundations with such members have reached replacement criteria and should be targeted for replacement as soon as possible. otherwise it will be necessary to replace significant steelwork. As discussed in subsection 2. This means there is a 6. 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. half the grillages were in better condition than the ground-line steel. On balance. It assumes a linear degradation rate from the original installation date (at condition assessment 100) to the most recent ground-line condition recording.3. However. but the members have not yet reached replacement criteria. Condition assessment scores less that 30 would require some replacements and more extensive preparation works. we have created a model to predict current and future grillage condition. and in 93% of cases it is within 20 condition assessment points. because definitive condition information cannot be readily observed. then continues linearly to forecast future condition.4.000 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. Propping a tower and removing members increases cost significantly.2. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. Foundations with a condition assessment score of 30 can be concrete encased without the need for member replacements. Generally. Page 28 of 58 . Ideally. The model also includes grillage foundations that have had their ground-line interfaces refurbished. 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. At a condition assessment score of 40 the galvanising is gone and there are initial signs of metal loss. In 80% of cases it is within 10 condition assessment points. investigations carried out on close to 1. a conservative approach will be adopted. We have good ground-line condition data for every foundation. and a 3.2.02 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. grillages should be encased in concrete before the condition gets too poor. In the late 1990s and early 2000s approximately 2. It also increases safety risk to workers and the potential risk of tower failure during the works. At a condition assessment score of 30.5% 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. Modelling grillage condition As discussed in subsection 2.5% chance that its condition assessment score is 20 or less. All rights reserved. Their ground- line condition is therefore no longer a good proxy for grillage condition. as such a condition assessment score of 40 is deemed the most appropriate condition to target for encasement.FL 01. TL Foundations Fleet Strategy TP.200 structures had their ground-line interfaces refurbished by blasting and applying thermal zinc spray. a condition assessment score of 30 to 35 is the optimal time to encase a grillage in concrete. with the other half being worse. metal loss has certainly occurred.

a further 50 will be refurbished somewhat early. Refurbishment volumes of 200 and 300 failed to achieve the grillage refurbishment objectives. soil conditions and construction are effectively equivalent at each property. Grillage refurbishment objectives and plan Based on available condition information and reflecting the optimum replacement timings. To achieve this. All rights reserved. By 2020 the condition of 880 grillages will fall below condition assessment 30. in general.  Life expectancy of an encased grillage is 120 years from the encasement date.400 have a condition assessment score less than 30. As of June 2013. 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. Plan to have no grillages with a condition assessment score under 30 by end of RCP2 (2019/20) 2. Over the next 20 years the condition assessment score of an additional 4. Of these 1.  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. it can be expected that the original installation date. However.  Degradation rate is linear. one key objective is to minimise disruption to stakeholders. as deliverability constraints and needs for scale efficiency will lead to foundations being addressed differently to that modelled. At the end of RCP2. based on condition data gathered from the previous 10 years. The data for these is somewhat less robust than for non-refurbished sites. approximately 3. This inevitably means that some works are carried out slightly earlier than they would be if based solely on condition.000 grillages are predicted as having condition assessment score below 40. 6 For the first objective the minimum required numbers are (1400 + 880)/7 years = 326/year. By that time. TL Foundations Fleet Strategy TP.FL 01. It is estimated that for every 350 foundations refurbished based solely on condition. They will be targeted for refurbishment before the end of RCP1 period. it is desirable to refurbish all grillages on a single property at one time. 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. Condition assessment data of the excavated steel will be collected while refurbishing the grillage foundations.000 grillages will fall below 40. the following condition-based objectives have been developed: 1. If the programme continues at 400 grillages each year. As an example. Beyond 2033. Page 29 of 58 .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. Modelling (see Appendix C) has determined that 350 grillage encasements each year is the optimum volume for the programme to achieve the above objectives. we will re-evaluate the appropriateness of the chosen plan. the youngest original grillage will be almost 80.6 It should be noted that 350 grillage encasements each year represents an ideal result. however they do pose a risk. Plan to have no grillages with a condition assessment score under 40 within 20 years (2032/33) 3. all grillages will have been refurbished by 2045.

000.1.2m.02 Issue 1 October 2013 Grillage prioritisation Prioritisation will be based on the priority matrix (see Figure 8). due to the heightened risk of them failing.500 2. Impact of refurbishment programme Figure 11 shows the predicted impact of the encasement programme on the number of at- risk grillage foundations. the average unit cost of a grillage encasement is $25. To date.ASSET HEALTH FOUNDATIONS . To complete approximately 400 grillages each year will cost an estimated $10.PLAN) (19/20 .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 4.000 500 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.000 1. which balances condition and criticality. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. All rights reserved.000 2.500 3. 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.4 for further details). FOUNDATIONS . Page 30 of 58 .FL 01. TL Foundations Fleet Strategy TP.ASSET HEALTH (19/20 . Grillages with a condition assessment score under 30 are a higher priority than a high-impact grillage just reaching 40. GRILLAGES AT OR BELOW CA 40 CA 31-40 CA 0-30 3.500 1.

The average out-turn cost for each foundation replacement is $47.2m. We will continue to investigate the capacity of existing foundations at critical sites and will strengthen those found to be understrength. from $25.000 to $170. The plan is to annually investigate foundations at 40 towers and strengthen an average of 8 each year over the RCP2 period. Studies have revealed that concrete foundations built before 1983 were usually designed based on very limited soil testing and often assumed soil properties. Urban developments and changing land use continue to increase the safety criticality of numerous sites each year. with the number each year being somewhat dependent on natural environmental events. An annual cost of $880. again resulting in approximately 20% being strengthened.000 (including design). which is discussed in subsection 4. with some 20% later being strengthened. The cost of pile foundations are derived using our volumetric forecasting methodology.000 has been allowed for each year from 2015 to 2020 for strengthening undersized pile foundations. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.1. leading to occasional installation of undersize foundations. Based on 47 pile foundation replacements over RCP2. 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.000 at each site. Page 31 of 58 . and those in rivers which have degraded to a point where replacement is warranted. this equates to a total cost of $2. Undersized foundation strengthening Strengthen undersized foundations in all critical locations to minimise the risk of tower failure due to overloading. which is discussed in subsection 4. Replace/Refurbish Pile Foundations Replace or refurbish pile foundations based on condition.4.1. Over the past 10 years. The cost of pile foundation strengthening has been derived using our approach to volumetric forecasting. This work is required to support safety and reliability by preventing structure collapses due to foundation failures. In the 1990s several hundred safety critical sites were investigated.000. TL Foundations Fleet Strategy TP.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.4. All rights reserved. Pile foundation replacement generally focuses on sites susceptible to erosion (where the land is unstable). Similar investigations have been carried out in recent years. Costs to strengthen concrete foundations vary considerably.FL 01. with an average cost of $105. an average of five pile foundations each year have required replacement.

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. Based on a forecast of 64 bridge replacements over RCP2. TL Foundations Fleet Strategy TP. Planning of all foundation works takes into consideration relevant site strategies. The average annual expenditure on access track bridge replacements over the last five years is approximately $1.02 Issue 1 October 2013 Bridge replacements Replace access corridor bridges based on condition.1.FL 01. Prioritise foundation works Prioritise the refurbishment and strengthening of foundations taking into account existing condition. with the scope and cost estimates becoming more accurate as the project becomes more refined. asset criticality and other factors. Access routes must be maintained so that. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. Our technical standards for bridges rely on the Transit NZ Bridge Manual.0m and this is predicted to continue through RCP2. 4. All rights reserved. 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). and existing bridges may need to be upgraded or replaced to meet our requirements. 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. Page 32 of 58 . The landowners requirements for access and load-bearing capability may be significantly less than ours. as a minimum. This optimisation approach seeks to ensure that works are deliverable and undertaken in an efficient and timely manner. and any potential synergies with other projects.0m. minimisation of required outages and resources. The main purpose of this strategy is to ensure continuing safe and efficient access to transmission lines for maintenance and project works. the access tracks and bridges can safely support access using conventional 4WD vehicles. we estimate a total expenditure of $6.3 Integrated Works Planning Our capital governance process –IWP – includes the creation of business cases that track capital projects through three approval gates. The IWP process integrates capex across a moving window of up to 10 years in the future.

TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. Ensure foundation works are scoped to achieve P50 Ensure foundation project estimates are developed and scoped to achieve P50 cost value. Historically.1. This feedback-based process is used to derive average unit costs for future works.FL 01. This has now transitioned to the central cost estimation team. The P50 cost value is an estimate of the project cost based on a 50% probability that the cost will not be exceeded.1. This strategy supports delivery of enhancement and development projects discussed in subsection 4.2 for further details on how this is applied to replacement projects. which uses the cost estimation tool Transpower Enterprise Estimation System (TEES). 4.02 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. TL Foundations Fleet Strategy TP. the expected cost of a programme of similar projects is of more interest than the costs of projects that are estimated separately.1. It ensures that all re-conductored lines and structure foundations on uprated lines where loads are increased comply with current loading and capacity requirements. P50 is an estimate of the project cost based on a 50% probability that the cost will not be exceeded. Page 33 of 58 . All rights reserved. Cost estimates for volumetric capital projects are developed on the basis of tailored ‘building blocks’ informed by actual cost of completed.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. This enhances safety and reliability. They are categorised as volumetric works for estimation purposes. that is. equivalent historic projects. the P50 estimate is based upon an equal chance of project overruns or under runs up to the finalisation of the project scope. In a general sense. 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. See subsection 4. Most foundation works are repetitive with similar scopes. cost estimates for foundation works were developed using proprietary systems.1. Further details on our cost estimation approach can be found in the Planning Lifecycle Strategy document.

Page 34 of 58 .01) specifies higher-return period weather events for critical assets than for less critical ones (such as higher reliability level for more critical assets). Replacement foundation design Design replacement foundations to carry the anticipated design loads of likely future upgrades. Designing replacement foundations taking into account anticipated design loads of likely future upgrades is prudent. Foundation design Ensure assets with high safety or Grid criticality are designed and maintained to be more reliable than less critical assets. as little more time is required to dig a bigger hole. the only additional cost is for extra concrete. The following discussion focuses on delivery issues that are specific to the foundations fleet. Procurement issues relevant to the foundations fleet during the RCP2 period are set out below.2 Delivery Once planning activities are completed.2. slightly longer grillage members are required. There are significant economies of scale in increasing foundation capacity at the same time as undertaking foundation encasement/replacement. For concrete encasement.02 Issue 1 October 2013 4. see The Sourcing. a standard grillage or other foundation type may be considered. sustainable asset management planning and delivers on the objectives relating to network and cost performance. 8 While design activities are undertaken during the Planning Lifecycle. Supply & Contracts Approach (2011) and the Delivery Lifecycle Strategy. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. 4.FL 01.2. the installation cost is relatively constant. 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. 4. For the grillage replacement option. All rights reserved.DL 12.1. but. TL Foundations Fleet Strategy TP. again. the design process8 aims to ensure appropriate site-specific designs are used.2 Procurement For more details of our general approach to procurement. Capex projects move into the Delivery Lifecycle. Delivery activities undertaken are described in detail in the Delivery Lifecycle Strategy. Where concrete is not easily transportable to a particularly remote location. This is in line with standard international practice. As discussed above in subsection 4.1 Design When applied to foundations.2. Our transmission line loading standard (TP.

selected tender. In particular. landowner disruption and system outages are minimised.1. All rights reserved. The preferred procurement method is sole source. Page 35 of 58 . Locally based contractors have geographic knowledge of the area and so are more suitable to work in rugged terrain.02 Issue 1 October 2013 Award contractor work on a sole source ‘yours to lose’ basis. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. and second preference. Selected projects are put out to tender based on the availability of the expertise required to perform the project.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. Award contractor work by geographic locations on a sole source ‘yours to lose’ basis. 4. labour and material constraints. an integrated programme view is taken rather than evaluating the sum of the individual works. 4.3.3 Operations The Operations Lifecycle phase for asset management relates to planning and real time functions. Performance-based contracting will be used to provide incentives to contractors to align their objectives with ours. TL Foundations Fleet Strategy TP. 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 following discussion focuses on operational issues that are specific to the foundations fleet. Foundation work is mostly of a volumetric nature. work is packaged to maximise efficiency and ensure that any travel time. Where practicable. This strategy aligns with the objective to minimise system disruptions and maintain reliability. Project deliverability Ensure planned projects are deliverable within available financial. This subsection sets out how IWP is applied to tower and pole project delivery. Under the IWP processes. This strategy aligns with the objectives in relation to cost optimisation and system performance and reliability. This strategy aligns with the objective to control costs by minimising supplier diversity.2. Our IWP processes deliver on this strategy.FL 01. Package work Package works into blocks of consecutive structures and ensure multiple works are carried out at one site simultaneously wherever possible. Operational activities undertaken are described in detail in the Operations Lifecycle Strategy.

 Emergency Management Team: Maintain readiness of emergency management team with communications routes to Civil Defence and to site works contractors.  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. and put in place as required. When works do require an outage. floods and landslides. 4. corrective maintenance. located in many different environments.1 Outage Planning Power system outages for preventive maintenance. Very few foundation works require outages. including emergency restoration structures.3. but may ask others for help following multiple structure failures. TL Foundations Fleet Strategy TP. To ensure rapid network restoration times. it is inevitable that foundations and their towers will occasionally fail during extreme events such as high winds. Foundation works outage planning Plan to minimise disruption to customers for foundation works that require outages.3. Page 36 of 58 . including emergency restoration structures. This strategy aligns with the stakeholder and network performance objectives. we employ the following contingency strategies.  Business continuity plan: Maintain the business continuity plan. 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).02 Issue 1 October 2013 4. We ensure that asset specific emergency plans are developed for critical assets. All rights reserved. Grid operations identify requirements for outages (including reclose blocks) and manage the planning of outages and reclose blocks.FL 01. Planning for failures is essential so that service can be restored relatively quickly when failure occurs. Maintain contingency response resources Have sufficient plans.2 Contingency Planning With thousands of towers on the network. Yearly drill for significant outage communications and process. and replacements must be planned to minimise disruption to customers. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. Resources must be sufficient to manage contingencies using a tiered response where local contractors rectify failures of one or two structures. We will follow the strategies set out below when planning outages for foundation assets. we coordinate with stakeholders to ensure that any unavoidable system disruptions and outages are notified well in advance so that affected parties can prepare. Continue the business continuity plan. This strategy delivers on the objectives in relation to System Performance and Reliability.

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

4. Condition assessment is carried out in line with TP. A ground- based patrol visits each structure foundation to identify any defects that could pose a risk to the structure integrity. even if this is scheduled some time after the initial need for action is identified. 4. which is expected to provide clearer reporting of data and trends. As discussed in 2. New foundation assets are first assessed just prior to expiration of the defects liability period.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. It also allows extrapolation of the assessed condition into the future. tower line assets are generally assessed every 8 years. When significant defects are identified a maintenance job is raised to rectify the issue.2 Corrective Maintenance Corrective maintenance includes unforeseen activities to restore an asset to service. The condition assessment (CA) programme monitors and records the condition of transmission line structures. scouring and subsidence  third party excavation or construction around tower foundations. prevent imminent failure and address defects. At June 2013. and enables planning to take into account the impact of varying environmental ageing factors. the assessment frequency is reduced to 4 years. Such defects include:  severely damaged foundations  geotechnical risks due to slips. Sites with unusually rapid degradation or those with higher criticality may be assessed more frequently. The frequency of patrols will be assessed based on site or corridor safety criticality. high-quality data is collected to inform asset planning and decision making.17B Transmission line condition assessment Part B: Structures.FL 01. The programme provides a basis upon which replacement or maintenance options can be investigated. It includes the required follow- up action.based asset management information system. nationally consistent. Thereafter. This strategy supports the network performance objectives for foundation assets. however this is being replaced with a MAXIMO. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. If the condition assessment score is less than 50. All CA data is currently stored in our maintenance management system MMS. By the end of 2013 all CA data will be on the MAXIMO system. TL Foundations Fleet Strategy TP. We will continue to develop and refine the existing condition assessment process to ensure relevant. Foundation condition assessments Carry out regular foundation condition assessments. Line patrols are generally performed once a year on every transmission line asset.3.2. conductors and hardware. 5%–10% of individual towers and pole structures are on partial (half cycle) assessments. condition assessments are carried out on a cyclic basis and entail a detailed inspection of the structure and span. make it safe or secure. All rights reserved.SS 02. foundations. The assessment produces a condition assessment score for various components and a defect list. Page 38 of 58 .

Activities include:  Fault restoration: unscheduled work in response to repair a fault in equipment that has safety.9 Timely repairs reduce the risk of failure.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. All rights reserved. TL Foundations Fleet Strategy TP. 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. Corrective maintenance has historically been categorised as repairs and fault (response) activities. improve redundancy and remove system constraints by maximising the availability of assets. Repairs include the correction of defects identified during preventive maintenance and other additional predictive works driven by known model type issues and investigations. For the purposes of system performance and safety. environmental or operational implications. 9 Where the number of potential repairs is deemed sufficiently high. including urgent dispatch to collect more information  Repairs: unforeseen tasks necessary to repair damage. 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.FL 01. Corrective works may be urgent and if not completed for a prolonged period. Repairs We may repair foundations where a fault has been identified that could potentially result in a failure or when a failure has occurred. Page 39 of 58 . a Maintenance Project will be instigated to undertake the repairs works. 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. This supports our network performance and safety objectives. 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. When the cause is determined. reduced network reliability may result. In both cases the repairs are carried out to support the safety and network performance objectives. it is critical that this be established as quickly as possible. The purpose of a fault patrol is to establish if the circuit can be safely re-energised and determine the cause of the fault. repairs are planned and implemented commensurate with the safety risk and asset criticality.

Some 1.3 Maintenance Projects As discussed in subsection 2. mitigating safety and environmental risks. Maintenance projects would not be expected to increase the original design life of the larger assets. maintenance projects typically consist of relatively high- value planned repairs or replacements of components of larger assets.FL 01. as such. their failure has the potential to result in a structure collapse with significant implications for safety and reliability. The purpose of this strategy is to ensure the integrity of the foundation system is maintained and lifecycle costs are minimised.2. All are subject to corrosion. The drivers for maintenance projects include asset condition.type foundations is porous and has led to mortar crumbling. Refurbishment by blasting and painting has proven highly successful.4.5. but they typically do not extend far into the concrete (<20mm). Refurbishment selection is based on the minimum condition assessment score of the four leg-based scores collected at each site. All rights reserved. Maintenance jobs are typically run as a project where there are operational and financial efficiencies from doing so.300 baseplate connections currently have a condition assessment score less than 50 (see subsection 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 during refurbishment).  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. We periodically review refurbishment criteria and designs to ensure appropriate practice is being employed. TL Foundations Fleet Strategy TP. Connection component refurbishments Refurbish corroding baseplates. The typical threshold score of 50 before any significant rusting or loss of section is visible.  Baseplate /anchor bolt: Poor-quality dry-pack mortar originally used under baseplate. In extreme TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.3). 4.2. Foundation connection components comprise two types. and to improve performance. their refurbishment is considered a maintenance project activity. anchor bolts and cast-in stubs at a condition assessment score of 50 prior to onset of significant rusting.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. Over the RCP2 period we intend to implement the following maintenance projects on the foundations fleet. Regardless. Page 40 of 58 .

All rights reserved.4. we will also complete the marine foundation refurbishment works on the HEN- OTA-A line that began in RCP1. 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.FL 01. The estimated cost of this work is $700.3). these connections will require periodic paint maintenance at a repeat cycle of between 12 and 20 years depending on the site environment. which equates to an annual average expenditure of $200.5m. Some 670 stub connections currently have a condition assessment score less than 50 (see subsection 2. Foundation works are planned to protect these foundations from chloride ingress during RCP2.900. Marine foundation refurbishment Refurbish specific foundations in marine environments. The total expenditure for this strategy is $1. this equates to an annual expenditure of $3.000 for each tower. Transmission line tower foundations are occasionally located in marine environments.2.000. The work is planned for 38 sites on three South Island assets: AHA-OTI-A.300 for cast-in in-situ leg refurbishments. DOB-TEE-A and BLN-KIK-A. Waterway protection works Complete waterway protection work on defective pole foundations in riverbeds.000. TL Foundations Fleet Strategy TP. During RCP2.000. Estimated costs over RCP2 are $1. the steel cleaned. This work has an estimated cost of $600. This equates to an annual average expenditure of $260.0m. 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. property or the Grid. they are subject to additional degradation from tidal activity and chloride ingress attacking the reinforcing steel. Average out-turn costs for baseplate and anchor bolt refurbishments are $7. Refurbishment selection is based on the minimum condition assessment score of the four leg-based codes collected at each site. At 360 and 270 sites respectively.000 – an average of $75. and are $2. This is based on existing condition assessment information and expected degradation. Page 41 of 58 . 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. 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. As a result of this location. Once refurbished.02 Issue 1 October 2013 cases a small area of concrete is broken out. We plan to complete the programme of refurbishing existing foundations at sites where failure would pose significant risk to people. discussed in subsection 4.1. and the area repaired by grouting.3m over RCP2.

TL Foundations Fleet Strategy TP. Site reinstatement Reinstate decommissioned site foundations to their former natural forms. This includes all divestments that we believe have a 50% or greater likelihood of occurring during the timeframe. This subsection describes our approach to the disposal of assets within the foundations fleet. 4. we carry out diagnostic inspection and testing to investigate the cause of the failure.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. 4. Foundations may be replaced with new ones. recovery and recycling/disposal of materials. professionalism and safety. including requirements for foundation removal. We will monitor rehabilitated areas for a period of time after re-instatement. Page 42 of 58 . In the case of a failure. 4. The total number of assets to be transferred represents 4% of the total tower and 9% of the total pole fleet as at June 2013.02 Issue 1 October 2013 4. Work is to be carried out only by individuals TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013. Foundation divestment Divest foundations as part of transmission line divestments to customers. This information is fed into the management of the entire foundation asset fleet. All rights reserved.FL 01. we will follow appropriate decommissioning process.5.5 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. The approach is set out in detail in the Disposal Lifecycle Strategy. 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.5.2 Divestment Implementation of divestment is primarily the change of ownership. 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. tested and operated to high standards of skill. Decommissioned site foundations should be re-instated to their former natural forms to allow the land to recover. All towers will have associated foundations and these will be divested with the tower structure. This process and its justification are described fully in the Disposal and Divestment Lifecycle Strategy.6 Capability We require grid assets and equipment to be maintained. Consistent with environmental objectives. We are continuing with the transfer of a number of assets at the fringes of the existing Grid to our distribution business customers.

The current project to transition to the MAXIMO-based asset management information system will include a review and cleansing of data. improved guidelines will be developed including more photographic examples where relevant. 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. condition data and investigation reports. All rights reserved. Quality condition data is also required.02 Issue 1 October 2013 with competencies that are both appropriate and current (see TP. including root cause analysis. We plan to enhance the failure and incidence records system to improve consistency and usefulness of the data.20 Minimum Competencies for Line Maintenance.6. Data quality and completeness will continually be reviewed and amended as required to ensure a high-quality dataset is maintained. To improve condition assessment consistency. 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.FL 01. and to protect the public and their property from harm. condition and performance. moisture contents. Comprehensive records that cover the original installation of a foundation structure and any subsequent modifications are vital to enable quality asset management decisions.SS 06. TL Foundations Fleet Strategy TP.1 Asset Knowledge Robust asset knowledge is critical to good decision making for asset management. Maintain up-to-date asset records Maintain up-to-date records of all foundation asset attributes. Ensure the modelling includes lessons learned from the refurbishment programme in relation to observed degradation in various soil types. 4. type test reports. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.25 Minimum Requirements for Transpower field Work). Continue the development and refinement of models to predict the asset health of foundations. Page 43 of 58 . land use etc. some fields are currently incomplete. The capability strategies are described under three headings:  Asset Knowledge  Risk Management  Training and Competence. design reports. particularly for grillages. This section describes the approach used to ensure that these competencies are present in those undertaking work on the foundation and access assets. and TP.SS 06. Revise building blocks on an ongoing basis using costs from completed works and forecast innovations and improvements. Data must include details of exactly what is installed.

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.6. We maintain a minimum baseline of retained skilled workforce: engineers and site works operators who understand the physical assets. Risk-based options evaluation framework Develop a risk-based framework and associated tools for evaluating foundation investments. TP.20 Minimum competencies for lines maintenance  TP. As outlined in subsection 2. We will develop an improved risk management framework and tools that can be used across the foundations fleet to evaluate investment options. 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.SS 06. and will allow risk assessments to be more readily communicated to internal and external stakeholders. All workers must hold appropriate competencies to work on our assets in line with the service specifications.25 Minimum requirements for Transpower field work. The risk model will specifically consider uncertainty in the inputs to risk-based decision making. All rights reserved. 4.20 (Minimum competencies for lines maintenance) and TP. Risk management processes will be made more robust and systematic.SS 06. TL Foundations Fleet Strategy TP. Foundation worker competencies Adhere to the following service specifications.02 Issue 1 October 2013 4.6. In recognition of this. The strategies below discuss how we plan to progress this in regards to the foundations fleet.FL 01.25 (Minimum requirements for Transpower field work). Knowledge of foundation condition is crucial to the assessment of options for foundation replacement and refurbishment.3 Training and Competence We have two service specifications that define the competency requirements for working on transmission line assets.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. Page 44 of 58 .SS 06. including foundations:  TP. 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.3.SS 06. Understanding and modelling uncertainty then becomes an increasingly important element in risk management decision making. particularly given the consequences of foundation failure on transmission line performance. we are developing asset health and criticality frameworks to improve and integrate our risk-based asset management. TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.2.

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

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

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

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

FL 01. TL Foundations Fleet Strategy TP. Appendices | page 49 . All rights reserved.02 Issue 1 October 2013 Figure 15 shows grillages at a condition assessment score of 40. Figure 15: Grillages at a condition assessment score of 40 TL FOUNDATIONS FLEET STRATEGY © Transpower New Zealand Limited 2013.

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

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

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

 Prioritisation as shown in the matrix in Figure 8.2.000 1.500 1. no grillages with CA less than 30 by 2020.000 500 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 2013.1. Subsection 4. Figure 16 shows the effect of the encasement plan on grillage condition. then continues linearly to forecast future condition. TL Foundations Fleet Strategy TP.  Plan fails to meet the objectives stated in section 4. The following two sections show the impact of refurbishing 300 and 200 tower grillages each year.2.500 3. that is.1.2.4 and 4. to the most recent ground-line condition recording. but where it is prudent to refurbish them at the same time as the others to minimise landowner disruption).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.02 Issue 1 October 2013 C GRILLAGE ENCASEMENT MODELLING As discussed in sections 2. It assumes a linear degradation rate from the original installation date (at condition assessment 100). Appendices | page 53 . GRILLAGES AT OR BELOW CA 40 (300/YEAR) CA 31-40 CA 0-30 3. a model has been created to predict current and future grillage condition and asset health.500 2. All rights reserved.1. Encase 300/Year Key points of alternative plan 300/Year:  Target 300 grillage encasements each year.FL 01.000 2.

ASSET HEALTH (19/20 . no grillages with CA less than 30 by 2020 Figure 18 shows the effect of the encasement plan on grillage condition. GRILLAGES AT OR BELOW CA 40 (200/YEAR) CA 31-40 CA 0-30 3.500 1. Appendices | page 54 .1.2.02 Issue 1 October 2013 Figure 17 shows the effect of the programme on foundation asset health/remaining life at the end of RCP2.000 1.FL 01.  Plan fails to meet the objectives stated in section 4.500 2. All rights reserved. FOUNDATIONS . that is.  Prioritisation as shown in the matrix in Figure 8.300/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.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. TL Foundations Fleet Strategy TP.000 2.500 3.

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.FL 01. TL Foundations Fleet Strategy TP.02 Issue 1 October 2013 Figure 19 shows the effect of the programme on foundation asset health/remaining life at the end of RCP2. All rights reserved. FOUNDATIONS . Appendices | page 55 .ASSET HEALTH (19/20 .