As New Zealand’s Army’s central stock holding unit, 1 Base Supply Battalion(1BSB) was responsible for managing and providing depot-level storage of New Zealand’s Military’s stock of land equipment and spares. Despite having this responsibility since 1920, 1BSB and its predecessors had always struggled with providing suitable warehousing infrastructure and made do with the available storage infrastructure.
With no purpose-built storage accommodation, from 1920 to 1940, the NZAOC Main Ordnance Depot (MOD) would utilise up to one hundred camp administrative and accommodation structures as its primary means of warehousing. Relief was provided in 1938 when contracts were issued to construct a modern warehouse utilising the most modern of methods and materials. The New warehouse, later known as Building 73, would be constructed using reinforced concrete and designed with nine bays that allowed the loading and unloading of Trains on one side and Motor Transport on the other. The design and layout of building 73 would be utilised as the model for new warehouses that would later be constructed at Burnham and Waiouru.
Although Building 73 provided a considerable increase in storage capability, wartime demands soon necessitated further increases in storage infrastructure, resulting in the construction of Building 74. Building 74 and the warehouses constructed in Burnham and Waiouru were close facsimiles of building 73, with the main exception that it was constructed out of wood instead of reinforced concrete due to wartime constraints.
The wartime expansion of the New Zealand military would see the MOD exponentially expand to cope with the influx of military material with additional buildings constructed in Trentham and sub-depots also established a Mangere, Wanganui, Linton Camp, Gracefield and Wellington.
Peace in 1945 would bring little respite as stocks were centralised at the MOD, requiring further expansion of the MOD warehousing infrastructure. To meet this need, five warehouses that were built for the United States Forces at Lower Hutt, were disassembled and re-erected at Trentham by September 1945. Additionally, the RNZAF Stores Depot constructed at Mangaroa in 1943 was handed over to the MOD in 1949.
Over the next forty years, the warehousing infrastructure at Trentham would change little, with a 1985 NZDF report identifying many deficiencies leading to significant upgrading of Trentham’s warehousing infrastructure.
In one of the most significant warehousing infrastructure investments since 1939 and the first modern warehouse built for the RNZAOC since 1972, Building 75, a high stud warehouse capable of holding 3700 pallets, opened in 1988. Although a significant advancement in warehousing capability, the new warehouse had limited space for outsized items. Additionally many other warehousing functions such as packing and traffic remained in Building 73, so further work was required to enhance the functionality of 1BSBs entire warehousing capability.
With trains no longer utilised for the delivery and dispatching of stores, the rail lines between Building 73 and 74 had long been redundant. By removing the rail line and raising the ground level between the two buildings, additional storage spect of almost two square kilometres, protected from the elements by a 200 x 13-meter roof, was created. At the southern end, a loading ramp was constructed to allow the loading and unloading of trucks, with angled ramps at either end allowing the movement of vehicles along the length of the new storage area. Opened on 2 November 1989, the new warehouse was christened as “the Cave.” The Cave allowed the more efficient transfer of stores to and from the storage areas in Buildings 73, 74 and 75 to the receipt, selecting, packing and issue bays in Building 73.
The additional storage space allowed the storage of outsized items which had previously been stored at the Mangaroa Depot, which was subsequently decommissioned and handed over to NZDF Property Services.
The optimisation of storage space between the two buildings was so successful a similar modification would be constructed between two of 21 Supply Company’s 1950s era Warehouses at Linton, creating much-needed storage and office space.
 “New Army Ordnance Block Now under Construction at One of the Military Camps,” Evening Post, Volume CXXVIII, Issue 65, 14 Sept 1939.
 F Grattan, Official War History of the Public Works Department (PWD, 1948).
 “Organisation – Policy and General – Royal New Zealand Army Ordnance Corps 1946-1984,” Archives New Zealand Item No R17311537 (1946).
 “Assessment and Audit – Audit Files –  – Nzdf Bulk Warehousing,” Archives New Zealand Item No R24596003 (1985).