Mangaroa railway station war. After the war the depot was a disposal site for surplus stores until RNZAF use ceased in July 1949, at which time it is assumed that the site was transferred to the NZ Army for their use. Prior to the construction of the Rimutaka Tunnel, several proposals for a tunnel under the Rimutaka Ranges to bypass the Incline section involved tunnels with a western portal to the north-east of Mangaroa station. In 1898 a survey was completed for a tunnel between Mangaroa and Cross Creek. The idea received a great deal of attention, but ultimately went nowhere as such
Rimutaka Tunnel at that time. It was not until the 1920s that significant campaigning for a replacement again prevailed on the government. In 1921-22 a feasibility study was conducted, including distances and estimated costs. Several routes were considered, including variations on previous ideas, but nothing more was done at the time; although a deviation of "about 5 miles 48 chain" (9 km) as the Wellington-Napier Line (Rimutaka Deviation) "running generally to the south-eastward of the existing line" was authorised by the Railways Authorisation Act, 1924. The new Labour government of 1936 announced its intention to proceed with the Mangaroa to Cross Creek