by PVC and polyethylene materials. Originally copper was used extensively for service connections but these have largely been replaced by polyethylene. The variable demand for water throughout the day is met by automatic adjustment of pump output at the two water treatment plants and two service reservoirs on the Wither Hills, one for each of the two main pressure zones. The larger zone, all of Blenheim north of Hospital Road, is served by the 10,000 m Low reservoir, while the area south of Hospital Road is served by the3 5,500 m Weld Street reservoir.3 The area of Blenheim to the south of Hospital Road includes higher ground on the foot of the Wither Hills which requires the separate supply zone to maintain pressures. The Wither Road booster pumps transfer water from the main (low reservoir) zone to the higher zone (Weld Street reservoir). Three smaller reservoirs at Marlborough Ridge, Forest Park and Redwood Street assist with pressure and demand balancing to localised zones. Booster pumps are used to deliver water into these reservoirs. A legacy of private wells and relatively shallow depth to the aquifer encourages large non- domestic users to use their own private bores. The public reticulation is therefore predominantly used for domestic consumption. It is policy within Marlborough for industrial, commercial, special and large users of the Council schemes to be metered and pay volumetric water charges. 1.5.3 Picton Supply Picton's water supply was first developed in 1891 when a dam was installed in the Waitohi Stream catchment. Water was delivered into the town via 225 mm trunk main installed in 1907 from the dam to Oxford Street. In the 1920s Humphreys Dam was added to the system. By the 1950s a new source of water was needed to meet the demand of a local freezing works and the growing demands of Picton town. A new impounding dam and reservoir were constructed in the Essons Valley. A 225 mm cast iron water main providing a direct supply from the new Barnes Dam to the freezing works was completed in 1952. The freezing works had paid the cost of the development and were given priority use of the water. However, a 1958 agreement between the freezing works and Picton Borough Council allowed a public supply from Barnes’ Dam whilst there was sufficient water for both. When water levels dropped below a pre-determined level the Borough supply was cut off and the public reverted to water from the Humphries’ and Williams’ Dams. In 1984 the freezing works closed and Barnes Dam became available exclusively for the municipal supply. In 1975 the Borough developed a new bore water source at Speeds Road, Koromiko 8 km south of Picton. Three bores abstract water from a shallow aquifer. It was decided the most cost effective water supply for Picton would be utilizing Barnes Dam with Speeds Road supply as a backup. Today, the early dams are no longer used and the Speeds Road bores and the Essons Valley water treatment plant (Barnes Dam) supply Picton's water. Both supplies are required to meet demand during the summer peak. However the impounded water in Essons Valley can suffer from qualitypoble s during the summer if the stored water stratifies and algal growths allowed to bloom. In these circumstances the Speeds Road bores becomes the sole source for the peak demand period. The Speeds Road supply has proved a very reliable source of water. The only exception was the prolonged dry spell of 2000/01 when water abstraction was reduced. Speeds Road wells are now more drought resilient. The wells have been re-drilled and deep sumps provided to house the submersible bore pumps deep below the water level. The water from the Speeds Road bores is disinfected with chlorine and the pH is raised by lime dosing before being pumped to the main Elevation Reservoir on the southern edge of Picton. Dual raw water mains feed water from the Barnes Dam by gravity to the Essons Valley treatment works. During 2011 the Essons Valley WTP was upgraded to improve the coagulation and flocculation of the raw water to enhance the filtration, the addition of ultra violet disinfection Page 8