Marlborough District Council Roading Assets - Activity Management Plan 2015 - 2018 SECTION 1 EXECUTIVE SUMMARY 1.6.4.4 Asset Maintenance and Renewal Asset maintenance and renewal typically consists of three levels of intervention: Routine maintenance Component replacement Renewal (replacement of the entire structure) 1.6.4.4.1 Routine Maintenance Routine maintenance is typically minor in scope and complexity, and entails timely replacement of consumable components (surfacing, handrails, guardrails, signage etc.) and maintain adequate drainage (removal of deck detritus, waterway blockages etc.). Routine maintenance typically addresses issues that ensure safe use of the structure and have no relation to level of service (LOS). 1.6.4.4.2 Component Replacement Component replacement describes the activity of replacing discrete structural components with new components while retaining others. Component replacement can be an isolated replacement (i.e. a bearing or expansion seal) or an extensive replacement (i.e. a timber superstructure may be replaced in its entirety) but does not intend to improve the LOS or modernise the structure. The primary aim of component replacement is to maintain the current LOS, and maximise the useful life of the remaining original components. 1.6.4.4.3 Renewal Bridges are renewed when the structure reaches the end of its useful life, i.e. when the entire structure, or key irreplaceable structural components (such as main beams, pile caps and piles), are no longer economically serviceable at the required LOS. In economic terms, renewal should ideally take place when the discounted life-cycle cost of maintaining the existing bridge exceeds the immediate cost of renewal. However, constraints on expenditure often require the maintenance of a structure (often with restrictions in place) beyond the point in time where it is optimally economic to do so. 1.6.4.4.4 Levels of Service (LOS) In this discussion, LOS is considered to be a ‘structural LOS’, i.e. the load carrying capacity of the structure, rather than a general LOS that would take account of lane carrying capacity (congestion), safety criteria, ride quality, or the like. A stable LOS is considered a constant number of restricted bridges across the entire asset. The following LOS options are considered when establishing future budgets for the asset maintenance and renewal: i. Do nothing differently: deterioration of bridge structures tends to be gradual and predictable, therefore a continuation with the existing budget and management practice would result in a consistent LOS if the age spread and deterioration rate of the bridge asset was uniform. However in reality, bridge assets have generally been built during intense periods with highly differing materials with variable length of useful life. This variability produces spikes in required renewal activity (such as currently with numerous timber bridges approaching end of life). A do-nothing-differently regime does not have the flexibility to address this variability and will result in a decline in LOS during periods of high maintenance demand. Once LOS has declined it is typically difficult to justify a recovery, especially in more remote areas. ii. Status Quo: this option maintains the assets to their current condition and service levels. This requires continual reassessment and alteration of maintenance budgets or capital expenditure to address fluctuations in asset deterioration. This option assumes that the current condition and LOS across the entire asset is acceptable. 30 September 2014 Page 73 of Section 1