During the history of New Zealand Railways, all locomotives and rolling stock have reached or will reach a state of obsolescence. When the cost of scrap metal drops below an economic level, other uses for locomotives and rolling stock are found. Some were dumped in locomotive dumps to aid protection of the railway against erosion or soft ground. The geology of the Southland Plains is built upon the loose rock which has washed down from the
Southern Alps over many centuries. The loose rock and surrounding mud at the Ōreti River crossing at Branxholme provided an unstable formation for the railway lines running west of Invercargill to
Ohai,
Riverton and
Tuatapere. Initially large amounts of rock and other debris were tipped at Branxholme to stabilise the line, however, this did not stay in place, particularly after heavy rains and subsequent flooding. In 1927, when scrap steel was an uneconomic proposition,
New Zealand Railways started dumping obsolete steam locomotives at Branxholme to arrest erosion. Branxholme is located along the-then Wairio Branch (now the
Ohai Industrial Branch) at the point where the railway crosses the
Ōreti River. Due to the river coming alongside the railway in an S-bend before passing under the railway bridge, the railway embankment was prone to erosion caused by the flow of the Ōreti. Initial attempts to control this using large quantities of rock and other debris were unsuccessful, and so NZR decided to use old steam locomotives which had been withdrawn as a bulwark against this erosion. In 1927, NZR sent the hulks of fifteen stripped locomotives to Branxholme for erosion control purposes. The locomotives were moved into position and then were tipped by a steam crane into the river. The first to be tipped into the river was the hulk of P 133, which subsequently lodged on the bank above the river and had to be further tipped by the crane to fall into the river. During the tipping operations, the boiler of P 60 came loose from its frames, as this boiler had been taken from another locomotive but not secured in place as P 60 had been withdrawn from service and was to be stripped prior to dumping. The dumping also exploited a key weakness in the
V class locomotives, causing their frames to break just to the rear of the cylinders. Boilers from a number of classes of locomotives were also dumped, at the Invercargill end of the site. In the early 1950s, parts from several U class locomotives were dumped there, some of which have tentatively been identified as belonging to U 194. A number of old small-firebox boilers from the
BA class 4-8-0 tender locomotives and a 1,700-gallon tender was dumped here at some time between 1927 and 1955, by which time there are no further indications of any dumpings taking place. It is known that scrap-metal hunters have found the dumpsite previously as many of the locomotives have been partially gas-cut to allow access to their copper inner fireboxes and bronze bearings. This has often dictated what engines can be salvaged from the dumpsite. Since the final dumpings took place, the Invercargill city council has constructed a stop-bank near the dumpsite, allowing easier access by enthusiasts to the locomotives. ==Initial locomotive salvage==