Kaimai Tunnel
| Overview | |
|---|---|
| Line | East Coast Main Trunk Railway |
| Location | Waikato / Bay of Plenty, New Zealand |
| Coordinates | West (Waikato) portal: 37°41′57″S 175°50′46″E / 37.6991°S 175.8462°E East (Bay of Plenty) portal: 37°39′35″S 175°56′01″E / 37.6596°S 175.9335°E |
| Status | Open |
| System | ONTRACK |
| Start | Hemopo |
| End | Whatakao Stream |
| No. of stations | None |
| Operation | |
| Opened | 12 September 1978 |
| Owner | ONTRACK |
| Operator | KiwiRail |
| Character | Passenger/freight |
| Technical | |
| Line length | 8.85 km |
| No. of tracks | Single |
| Track gauge | 3 ft 6 in (1,067 mm) |
The Kaimai Tunnel is a railway tunnel through the Kaimai Range in the North Island of New Zealand. Since it was opened in 1978, it has held the title of longest tunnel, at 8.879 kilometres, in New Zealand, assuming this distinction from the previous title holder, the Rimutaka Tunnel. It is part of the Kaimai Deviation, which was constructed to bypass the old route of the East Coast Main Trunk Railway through the Karangahake Gorge (part of which has been preserved as the Goldfields Railway).
The Kaimai Deviation is a 24 km line between Waharoa and Apata, including several major cuttings, embankments and viaducts, while the tunnel makes up 8.85 km of this distance 5 km from the Apata end of the line.
In the first half of the 20th century, the disadvantages of the East Coast Main Trunk route through the Karangahake and Athenree gorges became starkly apparent. The capacity of the line was constrained by several factors; its length, severe grades of up to 1:50, sharp curves of up to 6 chains radius, and light 55 lb per yard rail which prohibited the use of the more powerful diesel locomotives. It was also an unreliable route, with frequent disruptions caused by slips.
Proposals to shorten the distance between Auckland and Tauranga were made as far back as the early 20th century. A line over the Kaimai Range was suggested in 1911 but was quickly dismissed as being impractical. In 1913, a 3.2 km tunnel was suggested, and in 1920 a survey was requested for a Kaimai rail route, though it would be many years before this happened.
In 1955, an investigation was made of the possibility of road and rail access to Mt. Maunganui from the Waikato including a 4 km tunnel, an idea that was enthusiastically supported by Federated Farmers, and later local news media. This led to the formation of the Kaimai Tunnel Committee.
Hopes for a timely start on such a line were dashed, when on 14 August 1958 it was announced that the project was to be deferred. A report that had been prepared on the subject stated that there was an insufficient volume of guaranteed traffic then or in the near future to justify the project at that time. Alternatives were mentioned, including a preferred 24 km route between Waharoa and Apata with a 9 km tunnel (essentially what ended up being the Kaimai Deviation). The budget for such an option was expected to be at least NZ$10.5 million. It was felt that there was still sufficient capacity on the existing line, and that the idea should be reviewed when demand required it.
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