Marlborough District Council Roading Assets - Activity Management Plan 2015 - 2018 SECTION 1 EXECUTIVE SUMMARY Programmed drainage enhancement under the renewal vote, with an annual expenditure in the order of $90,000, allows for the installation of additional drainage facilities such as kerb and channel and channel linings. 1.6.3.7 Drainage Facility Issues and Risks The wide spread of drainage structure types and conditions in the network pose particular problems for systematic management and timely intervention. This risk is best managed by retaining a robust inspection and maintenance regime backed by a renewal programme which seeks to raise the current culvert replacement equivalent to address an ageing asset stock while allowing for rapid intervention where damage is identified. Blocked culverts and subsequent flooding in the Sounds, have been the source of a number of historic successful claims against the Council. This is a high risk and the importance of the maintenance contractor inspecting, clearing and recording culvert activities cannot be over stressed. This is a definite risk where the Council is exposed and relies on its maintenance contractor to mitigate that risk through a rigorous inspection regime. This inspection regime is specified in the NOC 01 maintenance contract. Surface flooding during high intensity rainfall, occurs at a number of locations around Blenheim Township. Occasionally this flooding is caused by block sumps but generally it is caused by lack of capacity in the underlying stormwater system. A schedule of known flooding locations needs to be developed, and investigation undertaken in association with the relevant Council services section, to determine the cause and possible solutions to the problem. Due to the effect of viticulture development and land use changes, runoff characteristics have significantly changed (ref: MDC hydrologist advises a 10 year rain event produces equivalent to a 50 year flood event as a discharge i.e. time of concentration is reduced and flood discharge is increased). Culvert sizes will likely have to be upgraded and other facilities upgraded in areas of the network adjacent to vineyards. This problem is common within the Wairau and Awatere valley parts of the network and there will need be a significant consultation process including regional staff, developers and landowners to apportion cost and responsibility. Prior to rehabilitation works culvert capacities will be checked and replacement undertaken if under capacity. 1.6.3.8 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 drainage asset. 30 September 2014 Page62 of Section