Marlborough District Council Roading Assets - Activity Management Plan 2015 - 2018 SECTION 1 EXECUTIVE SUMMARY A full survey of retaining walls has been undertaken and valuations included in the asset valuation inventory. The maintenance of structures falls into two categories as follows: Reactive Maintenance (Routine Maintenance): reactive works to maintain Level of Service, e.g. repair or replacement of damaged or deteriorated components. Proactive Maintenance (Renewals): programmed renewal to avoid asset failure. Currently lifecycle management is achieved through the application of a maintenance contract specification which requires the Road Network Maintenance Contractor to have an inspection programme to monitor the condition of the walls and structures. The repair or modernisation of wall and support structures will be necessitated by a damage or deterioration situation and the timetable is indeterminate. Fords in particular are unlikely to require any significant structural renewal other than repairs after storm damage. The repair and upgrading of older or damaged cattle stops will be in consultation with the adjoining farmer to determine the continued need for such stock control. There is very little historical data on the cost and performance of cattle stops but the age of the asset when weighed against the light construction of many, indicates a programme involving maintenance required on 10 units per year and the reconstruction of a nominal two units per year over 25 years. Routine inspection reporting is expected to adequately address the need to signal an upgrade or replacement of a miscellaneous structure. Life cycle interruption due to damage will need to be addressed from within the contingency plan. Historically only an extremely small length of retaining wall has ever failed, indicating an optimised methodology is in place. 1.6.5.6 Cost / Financial / FWP A summary of the financial Forward Works Programme (FWP) for structures is appended to this section. The FWP is based proportionally on lump sum contract rates for current maintenance contracts. Council assesses that ongoing maintenance is sustainable given the expected life of these structures, and no changes are proposed within this AMP. The installation costs, programming and budgeting for miscellaneous structures construction, modernisation or replacement is currently on a case by case basis. Due to the relatively young nature of these assets this activity awaits the assembly of a more robust history before an assessment can be made on a FWP. This will be developed during the life of this AMP and has been included in the Improvement Plan in Section 14. 1.6.5.7 Miscellaneous Structures Issues and Risks The prime risk in the prediction of the life cycle or continued satisfactory performance of miscellaneous structures is the integrity of the buried components. As various structure types or components within those structures are repaired, the safe working life of critical components needs to be assessed and recommendations appended to the asset record of similar structures. Other risks to miscellaneous structures are associated with the performance of critical components under conditions where damage or unforeseen deterioration due to weather or mechanical impact has occurred. Mitigation of the risk involves the continued routine inspections and careful analysis of components found to have failed. The philosophy involved with construction of these walls, generally within the Marlborough Sounds, is a balance between costs and risk. For example minimal geotechnical investigation and specific design is undertaken but rather a standard methodology and robust design is used and adapted to individual sites, where it is then expected that a small percentage of walls may fail. Such failure is unlikely to be catastrophic nor involve excessive public risk. Failures are most likely to occur during extreme storm events, at a time when other road failures may occur. Reinstatement is then likely to occur at higher financial assistance rates than may otherwise apply, further reducing Council’s financial liability. 1.6.5.8 Disposal Plan Disposal is any of the activities associated with disposal of a decommissioned asset, including sale, demolition or relocation. During the life of this AMP there is no anticipation for disposal of any part of the miscellaneous structures asset. 30 September 2014 Page 79 of Section 1