Maraetai I
| Maraetai Power Station | |
|---|---|
 Location of Maraetai Power Station in New Zealand
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| Country | New Zealand |
| Location | near Mangakino, Waikato |
| Coordinates | 38°21′9″S 175°44′38″E / 38.35250°S 175.74389°ECoordinates: 38°21′9″S 175°44′38″E / 38.35250°S 175.74389°E |
| Status | Operational |
| Construction began | 1946 |
| Opening date | September 1953 |
| Owner(s) | Mercury Energy |
| Dam and spillways | |
| Type of dam | Arch dam |
| Impounds | Waikato River |
| Height | 133 m (436 ft) |
| Length | 87 m (285 ft) |
| Width (crest) | 11 m (36 ft) |
| Width (base) | 15.2 m (50 ft) |
| Spillways | 1 |
| Reservoir | |
| Creates | Lake Maraetai |
| Surface area | 4.1 km2 (1.6 sq mi) |
| Power station | |
| Commission date | September 1953 (Maraetai I) February 1971 (Maraetai II) |
| Type | Conventional |
| Hydraulic head | 61 m (200 ft) |
| Turbines | 10 × Francis |
| Installed capacity | 360 MW |
| Annual generation | 885 GWh |
Maraetai Power Station is a hydroelectric power station on the Waikato River, in the North Island of New Zealand. It is the fifth of the eight hydroelectric power stations on the Waikato River, and at 360 MW, is the largest hydroelectric station on the Waikato.
The station has two powerhouses - Maraetai I powerhouse is directly in front of the Maraetai Dam, while Maraetai II powerhouse is located 550 metres (1,800 ft) downstream of Maraetai I. Although both are completely separate, both powerhouses are operated as one power station.
Maraetai is owned and operated by Mercury Energy.
In early 1946, the Minister of Public Works Bob Semple, announced a full development of the Waikato River, with the first three stations planned at Okakuri, Whakamaru, and Maraetai. Although Ohakuri was chosen first, the choice soon shifted to Whakamaru as it would be the best location for transmission needs. However, more investigation had been done for the Maraetai site, and starting Whakamaru first would make it more complex to divert the river for Maraetai later, so it was decided to build Maraetai first.
Investigations into a hydroelectric station at Maraetai had been completed between 1940 and 1945. The site was in a deep narrow gorge, west of Tokoroa and 20 miles (32 km) upstream of Arapuni. Because of the narrowness of the gorge, the powerhouse took up the entire length of the base of the dam, meaning no orthodox spillway could be constructed. This meant that the spillway had to be designed as part of the diversion tunnel. The site was composed of volcanic ignimbrite, which had cracked extensively on cooling meaning extensive grouting of the rock was required.
Construction of Maraetai I began in 1946, with the construction of an access road from Tokoroa, and establishing services and accommodation for the workers of the dam. The service and accommodation camp formed the town of Mangakino, on the south shore of what would become Lake Maraetai. Problems were encountered right from the beginning - the Second World War had just ended, which meant there was a great deal of shortages of labour and materials. The Public Works department's work-force was less than two-thirds of its pre-war size, with thousands of vacancies not filled. Concrete and steel were also in short supply, as steel imports were less than half their pre-war levels, and local contractors could only produce two-thirds of the required amount of concrete. Combined with industrial unrest and the nature of the site, the target completion date of 1951 became less achievable.
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