plans were considered, including a replacement of the three systems with a vertical turbine and another larger vertical turbine, allowing better accommodation of the changing river flows. This idea, however, failed, as well as later plans to use a single generator with one turbine at either end, partly because of the difficult access to the station, leading over a single-lane suspension bridge which imposed weight and size restrictions. It was therefore decided in 2004 to go for a simple replacement of all three systems with new vertical turbines and associated generators, one each in 2005, 2006 and 2007. The work was undertaken by Invercargill firm Alltec Engineering Limited and the station now operates with three Swedish TURAB 2,566 kW vertical Francis turbines coupled to Spanish Alconza 3,183 kVA synchronous generators. At the same time, the original riveted pipelines were replaced by 1.6m diameter welded steel pipelines. The new equipment has increased the power to 2.6 MW from each of the turbines, operating at 94% efficiency. Maintenance requirements have dropped significantly with the new equipment. While most of the old equipment was scrapped the third turbine and generator as well as the generator of the second machine were found to be salvageable and were purchased by Clearwater Hydro of Tauranga. Once refurbished one unit was put into service in August 2011 at Speedys Rd, a small hydro-electric station near Waitomo in the Waikato. Strengthening of the dam Since 2003 the dam had begun showing signs of distress during earthquake events in the Fiordland area. Subsequent investigations revealed issues with the construction methods and the timber which had been used to strengthen the dam core. This timber was now rotten. As a result, in 2012 in order to reinforce the dam and improve general security, a downstream shoulder was added, the freeboard increased and the upstream face covered in rip rap to manage the impact of waves. Design The power station has a head of . The Monowai Dam is a low earth embankment built across the Monowai River forming the 31 square km Lake Monowai. In an arm of the lake, about 8.5 km from the powerhouse, four control gates control the lake level. Water flows from the gates down the Monowai River for some 8 km to a headpond area formed by a weir across the river. From here it is diverted via a long canal to a forebay. The