The electricity transmission network is important to the social and economic well-being of Aucklanders and New Zealanders.Under the National Policy Statement on Electricity Transmission 2008, council is required to identify and provide a buffer corridor below and around high voltage transmission lines and transmission towers/poles. These lines and tower/poles are owned and operated by Transpower New Zealand Limited and form part of the national electricity grid.The purpose of these buffer corridors is to manage subdivision and development within close proximity to the high voltage transmission lines and transmission towers/poles, in order to prevent risks to people and property; protect the electricity transmission network; preserve line access for inspection and maintenance and to protect amenity values. High voltage transmission lines pose a risk of electrical hazard in situations where development occurs too close to the lines and may result in injury to persons or damage to property. This can be either as a result of direct contact with the lines or where an electric arc (or ‘flashover’) contacts structures, such as buildings. Conversely, development in close proximity to transmission lines can pose risks to the electricity transmission network itself. These risks include ‘reverse sensitivity’ effects, a loss of security of supply through outages or physical damage to support structures, constraints on access to the line and support structures for inspection and maintenance purposes and inability to undertake line upgrades. There are three types of buffer corridors to manage subdivision and development in proximity to the transmission lines and transmission towers/poles: a. urban inner transmission corridor, which covers the area 12m (both sides) from the transmission centre lineb. urban outer transmission corridor, which is located between 12 and 32m (both sides) of the transmission linec. rural transmission corridor, which is 12m (both sides) from the transmission centre line.Urban inner transmission corridorThis corridor generally has more restrictions, particularly for activities sensitive to the effects of transmission lines, such as residential and care centres, than the outer transmission corridor and rural transmission corridor. However, in recognition of the level of built development and the need to provide landowners some flexibility in the urban inner transmission corridor, the Unitary Plan takes a more permissive approach to certain building works, such as alterations and extensions. This is subject to certain standards being met, including the maintenance of access to transmission line support structures and the requirement to meet the New Zealand Electrical Code of Practice (NZECP34:2001). This code sets minimum safe distances from transmission lines to protect people, property, vehicles and mobile plant from harm or damage from electrical hazards.Urban outer transmission corridorDue to the increased distance from the transmission lines and towers/poles, the Unitary Plan places fewer restrictions on development in the urban outer transmission corridor. Compliance with NZECP34: 2001 is still required in this corridor because electrical safety considerations may still need to be factored into some building proposals.Rural transmission corridorIn the rural transmission corridor there are generally fewer restrictions on development. This approach recognises the low number of buildings under existing transmission lines, the lower probability of development occurring under or near the transmission lines and towers due to the availability of land, and the need to provide flexibility for normal farming operations. However, like the inner transmission corridor, sensitive activities, such as residential dwellings, are restricted.