4.1 Physical Parameters BLENHEIM PICTON RIVERLANDSRENWICKSPRING CRKHAVELOCKANAKIWAOKIWISOUNDSSEDDONGROVETOWNGrand Total CC-RF 65,991 17,897 3,967 3,359 2,947 768 680 299 102 96,010 PVC 28,582 7,915 1,546 1,120 216 450 214 67 21 40,131 AC 14,519 590 23 19 45 15,196 EW 3,870 568 4 4,442 NOF 1,361 450 130 168 2,109 (blank) 297 641 246 38 332 88 1,641 UNKNOW 1,133 80 10 306 2 1,531 ST-SW 1,351 71 1,422 CC 1,007 42 190 153 1,392 ST 1,201 164 1,365 CC-SR 1,285 15 1,300 RC 1,204 1,204 CI 231 22 252 UPVC 229 229 NOVA 5 178 183 FTILE 171 171 ALU-F 62 58 120 AC-F 115 115 ST-GL 58 4 7 31 99 RIBST 83 83 DRUM 25 25 PE 100 22 3 24 VC 19 19 ALUFLO 17 17 MPVC 16 16 SP 4 4 Grand Total 122,711 28,640 5,538 4,951 3,385 1,441 849 818 332 258 176 169,099 Table 4 Pipe Material As a general rule human settlements establish in areas that take advantage of natural drainage channels for removal of stormwater. It is only as the urban area develops that it becomes necessary to install a more elaborate piped infrastructure to remove the surface water. The piped stormwater network is considerably shorter and younger than both the water and sewer networks. In Marlborough the central urban areas are commonly served by the original pipework whilst newer pipes are installed on the periphery as the towns expands. This can cause considerable capacity issues for growing settlements. The older infrastructure is often required to convey the stormwater flows from the increasing drainage area. The implications are discussed further under 4.1.1 Asset Capacity/Performance. Table 4 shows the composition of the stormwater reticulation network. Around 90% of the entire network is constructed of three materials – concrete, PVC and asbestos cement. Generally concrete is the preferred material for larger diameter pipes (225 mm and greater.) PVC has replaced asbestos cement as its modern equivalent. These two materials are more commonly used in the smaller diameters - up to and including 300 mm. Concrete is the oldest pipe material recorded in the current stormwater network. It has been used for at least 75 years in Marlborough. Over the years the method of manufacture has developed considerably. The early pipes were not reinforced and were cast in vertical moulds. Modern concrete pipes are now supplied as steel reinforced, centrifugally spun pipes, manufactured in accordance with NZS 3107. A variety of jointing methods, joint materials and linings have also been incorporated over the years. Asbestos cement was a popular material in the 1940s. Records show it was still being used into the 1980s. Modern plastics and particularly PVC were being introduced into the market in the latter part of the 20 century. Their acceptance was accelerated as the health risks associatedth with handling asbestos cement became more apparent. A recent CCTV survey revealed a concrete arch structure from the roundabout at the High Street/Redwood Street running north under Park Terrace. This was previously unknown. The Page 35