lowest operating cost per unit of desalinated drinking water of any desalination plant in Australia. This was possible because of energy efficient technologies and innovations throughout the plant. The plant's buildings have been designed to maximise natural light during the day and a selection of high thermal materials (e.g. solid precast concrete walls and insulation) to improve thermal properties, thereby minimising energy consumption. More specifically, solar photovoltaic cells have been placed on the reverse osmosis buildings for localised power generation. Each reverse osmosis building has an approximately 100 kW solar cell array providing a site capacity of approximately 200 kW at peak sun hours. The high pressure pumps feeding the reverse-osmosis membranes are the largest consumers of energy in the plant. Energy recovery devices are installed to harness the pressure in the saline concentrate stream and use it to pressurise some of the feed water. As a result, the high pressure pumps are only needed to deliver half of the water feeding the reverse osmosis system, reducing energy consumption in the plant by up to 40 per cent. Likewise, two turbine generators in the outfall tunnel take advantage of the plant elevation 50 metres above sea level. This mini-hydroelectric system is capable of producing 1,290 kW of renewable electricity which is fed back into the plant, reducing energy consumption by approximately 2.5%. Effects on marine life The lack of tidal movement for up to 2–3 days during dodge tides, which occur twice a month in Gulf St Vincent, reduces mixing of the water column. This raised concerns during the planning phase of the project about the potential effects of the brine discharge on benthic flora and fauna. Dodge tides and other local conditions were taken into account in the design of the outfall system. Discharge to the sea occurs via a 1,080 m undersea tunnel, with dispersal through one of 6 specially designed diffusers. Each diffuser has a head consisting of four duck bill valves that assist in maintaining high discharge velocity for optimum mixing, independent of plant operating conditions. Marine monitoring buoys placed at 100-metre radius from the outfall structures allow real time data monitoring via the plant control system, to assess performance against Environment Protection Agency discharge licence conditions. Monitoring of the surrounding marine environment started before construction of the plant began and will continue into the future to ensure no adverse environmental impact. Utilisation and controversy The