Función Disciplinaria En ejercicio de la función disciplinaria, se de-

of replacement only where the asset has no further useful output. The minimisation of wheel-timbered assets along the main lines means that the

Bournemouth main line is now almost completely free of such assets.

Context

The Wessex Route has 6 per cent of the national structures population and is distributed typically as 60 per cent masonry, 35 per cent metallic and 5 per cent concrete. The vast majority of masonry assets only require basic maintenance interventions to maintain the required capability and the concrete bridges tend to be modern and therefore in need of little investment.

The density of assets is skewed towards the Clapham delivery unit where significant parts of the railway are on elevated viaduct. High value tenancies in these arches can influence maintenance requirements and may lead to sub-optimal policy interventions which pay back through tenancy income.

The Woking delivery unit has a typical mix of assets.

The Eastleigh delivery unit has a high number of assets over water, and a risk of water scour, many of these have had remediation in recent years. Although wheel timbered structures have largely been eradicated from the main lines to Bournemouth and Portsmouth Harbour they are still prevalent on the suburban and rural lines.

Wessex Route policy in CP5 will be to focus on removing scour risk on the Eastleigh delivery unit and to target wheel-timbered assets.

Underline bridges are predominately wrought iron with several large truss structures forming

key intersections. Wessex Route has six discrepancy bridges, with four planned for removal by the end of CP4 and the remaining two will be renewed in CP5. There are currently 124 marginal assets and policy will focus on preventing marginal assets from becoming discrepancy. Over 80 per cent of Wessex’s underbridges are in the adequate category.

Overline bridges – Wessex Route has met most of its obligations under the Bridgeguard

programme and has only a handful of remaining assets that do not meet our obligation. These will not be resolved in CP4 and require negotiation with Local Authorities to resolve. The major risks in this portfolio revolve around cast iron bridges over the railway, their potentially brittle nature of failure and the fact that they are typically on private roads where surfacing is not as controlled as on the public highway. A number of these sites are planned for remediation in CP5.

Condition (of under and over bridges only) is measured using the Structures Condition Marking Index (SCMI), with 100 representing a bridge with no defects. The mean SCMI score is 65.

Minor Assets (primarily footbridges and culverts) – the Route has a series of standard

designed footbridges which fit into several family groups. The highest risks in these areas are the metallic lattice type bridges along the ‘coastal’ parts of the network where corrosion is an increasing issue. The replacement of a proportion of these is avoided by refurbishment.

Structure Type Number

Major structures Culverts 1,044 Footbridges 184 Former bridges 27 Retaining walls 932 Overbridges 674

Underbridges (incl viaducts) 1,207

Tunnel bores 31

Tunnel shafts 13

Tunnel portals 52

Total 4,164

Structure Age (bridges) Percentage of stock

145 yrs old or older 20%

110 – 145 years old 65%

51 – 110 years old 10%

CP4 activity

Interventions are aimed at preventing increases in safety or performance risk and the need for works is informed by regular structural examinations to report on condition and structural assessment to report on structural capacity.

The Enhanced Spend risk reduction programme will undertake painting, exposure of hidden critical element (HCE), and a number of scour protection schemes by the end of CP4. The schemes in this programme have been identified in line with CP5 policy.

Activity CP5

The interventions planned for CP5 are in line with Structures policy, recognising the following underpinning principles:

 Maintain the condition profile of the asset base from CP4 exit level.

 Deliver the Route’s licence conditions in terms of capability, so that routes that are currently published at Route Availability 8 remain capable of carrying that load or a negotiated network change is put in place. No permanent network changes are proposed in CP5 because of asset deterioration.

 Remove key risks emerging from archaic forms of construction.

A plan has been developed to remove fatigue susceptible wheel timbered assets and cast iron (non-ductile) assets. This is over and above current policy but represents a specific Wessex Route set of risks.

Structures maintenance requirements have been based on an increased intervention beyond CP4 levels to reduce performance risk on key pieces of infrastructure, such as London Waterloo – Basingstoke. The change in approach will see a ‘line of route’ approach adopted with planned preventative maintenance carried out. Recent evidence suggests that many assets in this corridor are experiencing higher than would be expected defect rates.

The interventions have been dictated by a correlation between Technical Risk (Condition) and Business Risk (Track Category) to try to make sure that the most resilient asset interventions are carried out on the appropriate parts of the Route.

It should be noted that the application of whole-life cost solutions and new policy interventions has been balanced over several control periods so full compliance with policy is not expected to be achieved by the end of CP5.

The critical asset base has been defined for the Route as assets that have low redundancy, such as cast iron overbridges. Other risk features within the network have been identified as assets with hidden critical elements, fatigue critical details and structural wheeltimbers. This programme aims to remove those that are significant to the Route’s performance. We plan to remove 12 wheel timbered structures in CP5. The most significant structures include those at the rivers Avon and Stour where bridge reconstructions will be needed, the rest are smaller span to be replaced with concrete decks.

No plans are included for works to the station fabric at London Waterloo, but a major

refurbishment of the bridge at London Waterloo throat is included in the structures work bank. This works is considered necessary in light of current plans, and is not linked to further HLOS required outputs for London Waterloo.

Key Assumptions underpinning the Structures Asset Management Plan

 36 per cent of the assets scoring Bridge Condition Marking Index less than 50 have been reviewed and the totals for interventions extrapolated from that. This will be refined and has been done as policy only emerged in the last few months. This has been balanced by an ‘intuitive’ bottom up workbank and a real review of structures with a Route Availability of less than 10.

 This plan includes works on the basis of current passenger and freight demand but it is recognised that increasing freight may impact on bridge fatigue, requiring increased levels of structures interventions.

 The level of deterioration of assets has been based on policy guidance, especially where assessments/condition data is not available yet.

 Only minor works will be identified from the HCE programme implemented in CP4 and the risk of structures requiring a major project is deemed small as high priority risk HCEs have already been undertaken.

 The impact of further changes around London Waterloo station has not been included in this plan on the basis that this would be a separately funded major project.

Civils expenditure (post efficient) in CP5

Civils 0 5 10 15 20 25 30 35 40 45

FY14 FY15 FY16 FY17 FY18 FY19

£m (12/13 price)

Buildings