Infrastructure Strategy Introduction implementing the stormwater strategy. The strategy is a detailed analysis of the The stormwater infrastructure is a reticulated network of pipes, channels, pump stormwater issues for the town and is a fundamental element of infrastructure stations and associated apparatus required to drain rainwater from residential, planning. The strategy groups many small drainage catchments throughout Blenheim commercial and industrial properties and surrounding land. The service is into 11 Stormwater Management Areas (SMAs.) Detailed, integrated action plans are predominantly focused on the urban areas where buildings and other structures disrupt being developed for each SMA which will meet the future requirements for growth in the natural flow paths of surface water drainage and hard surfaces, such as roofs and stormwater flows and quality standards. roads, prevent rainwater from being absorbed into the ground. The following table provides a summary of the Council’s stormwater systems Stormwater drainage relies on discharging rainwater to rivers and streams as well as man-made channels. As a unitary authority (with both regional and district council Area Length(m) Pump Stations responsibilities) the Council manages both the man-made stormwater pipes, drains ANAKIWA 849 and natural water courses. Close, coordinated management between the stormwater management staff and rivers and land drainage staff is essential to achieve an BLENHEIM 125,199 2 effective and efficient drainage of surface waters. This arrangement was incorporated in the Blenheim Stormwater Strategy, which was adopted in 2012. The strategy GROVETOWN 293 provides an integrated and holistic approach to stormwater management with clearly HAVELOCK 1,310 defined objectives to manage the quantity and quality of stormwater across Blenheim. OKIWI 822 The urban growth pockets identified to the north-west of Blenheim are in the PICTON 28,547 1 headwaters of many local creeks. Development of these areas, coupled with increased rainfall from climate change, needs to be managed carefully to prevent negative RENWICK 5,167 consequences downstream. RIVERLANDS 4,784 Many of the spring-fed creeks passing through Blenheim, and upland streams passing SEDDON 257 through the smaller settlements, have high quality water and pristine aquatic habitats. Increased public concern over the quality of New Zealand waterways has been SOUNDS 332 recognised through the National Policy Statement for Freshwater Management SPRING CREEK 3,385 (NPSFM). New developments include low impact design techniques for on-site treatment of stormwater. Infrastructure may need to be retrofitted to ensure existing ST.ANDREWS 323 stormwater discharges meet thenew level of service standards. GRAND TOTAL 166,134 The expectation of more intense storms as a result ofclimate change must be accommodated through a combination of larger pipes, channels and pump stations, overland secondary flow paths and specially designed detention areas that will hold back the peak flows, preventing downstream flooding. 1. Specific challenges for this asset Similar to water and wastewater assets, much of the underground stormwater 1.1 Stormwater quantity reticulation is reaching the end of its useful life and will need tobe renewed. A very significant peak of around a third of the total asset value (of$115m) isanticipated frmo Urban Growth around 2048 – just beyond the planning horizon of this strategy. The Marlborough Urban Growth Strategy has identified pockets of land to A collaborative working relationship between the Council’s Rivers & Land Drainage, accommodate the expected demand for housing over the next 25 years. For Blenheim Stormwater and Operations departments is proving to be an effective mechanism for a land area of around 160ha was identified to the north and west of the existing town. The natural drainage for these areas is from west to east meaning that the stormwater 2018-2028 Long Term Plan Page 201