Pipe Shed

This pipe in Methven, New Zealand, was cast in 1940 and then converted into a shed for storing explosives. It's one of about 800 pipes made for the Rangitata Diversion Race, or RDR, and it's the only one that's still visible today. It's considered a memorial to what was the largest public works project of its time, and Heritage New Zealand has registered it as a Category I structure.

The RDR was an irrigation project that started in 1937, led by engineer Thomas Beck. It was the biggest public works scheme in New Zealand then, meant to create jobs during the Great Depression. The main canal runs 67 kilometers from the Rangitata River to the Rakaia River. They had to cross several major rivers, and the land near the Surrey Hills proved unstable. In 1938, heavy rain caused a slip that damaged the canal, so it was rerouted and piped using inverted siphons.

These pipes were made in 1940 at The Birches, south of Mayfield, with eight started each day. They came in two sizes. The smaller ones, for river siphons, were 3.4 meters in diameter, 3 meters long, had walls 230 millimeters thick, and weighed 18 tons. The 723 larger pipes were 3.7 meters in diameter and length, with walls 250 millimeters thick, and weighed 28 tons each. Apparently, these were the second-largest spun reinforced concrete pipes in the world at that time, only smaller than those used for irrigation from the Colorado River and Boston's water supply. The minister of public works, Bob Semple, even drove his car into the first pipe laid at Surrey Hill.

The Public Works Department set up its RDR headquarters and a workers' camp here in Methven. To store explosives, one of these RDR pipes was installed at the camp, set on a pre-cast control gate as a base. Wooden wedges keep it from rolling, and concrete ends were cast to close it off. There’s a wooden door in one end, with a vent above it, and a wooden floor inside. It was also used to store concrete sometimes. The outside is in good shape, except for a crack above the vent, but the internal floor has deteriorated, and the door is a replacement.

This Pipe Shed is the only thing left from that work camp. The land is owned by Ashburton District Council and the area around it is used for grazing. It's kind of hidden from public view, surrounded by roads on three sides, but you can get to it through a gap in the bushes from Main Street or through the Garden Of Harmony, which is a reserve on South Belt. There was a plan to move it to a more visible spot next to the Mount Hutt Road Board building, which is Methven's oldest building. In 2025, the Pipe Shed was restored, with plans for it to be a feature in an extension of the Garden of Harmony, along with a decommissioned turbine from Highbank Power Station.

The Pipe Shed was listed as a Category I historic place on April 14, 2005. It's unique because round buildings are unusual, pre-cast concrete buildings are rare, and it’s the only visible pipe from the RDR. It’s also the only reminder of what was once a busy work camp, and its size really shows the technological achievement of the RDR project.