The United States Navy's Naval Operating Base, was a seaplane base in Bermuda, the original Naval Air Station Bermuda. Following the US Navy's take over of Kindley Air Force Base (subsequently retitled NAS Bermuda), the base was adopted to other uses as an annex to the new NAS Bermuda, the NAS Annex. Following the end of the Cold War, the base was closed in 1995, along with other US Naval, Royal Naval, and Canadian Armed Forces facilities in Bermuda.
Prior to American entry into the Second World War, an agreement was arranged between the governments of British Prime Minister Winston Churchill and U.S. President Franklin D. Roosevelt for the loan of a number of obsolete, mothballed ex-US Naval destroyers to the Royal Navy and the Royal Canadian Navy, in exchange for which the USA was granted 99-year base rights in a number of British West Indian territories. This Destroyers for Bases Agreement, a forerunner of the Lend-Lease Agreement, had the sleight-of-hand effect of placing the defence of those territories in the hands of the neutral USA, allowing British forces to be sent to the sharper ends of the War.
Although not part of this exchange, Churchill also granted the US similar base rights in Bermuda and Newfoundland, however no destroyers or other war material were received by Britain in exchange. The grants came as a surprise to the Colonial Government, when US engineers arrived in 1941 to begin surveying the colony for the construction of an airfield that was envisioned as taking over most of the West End of the Island. Frantic protests by the Governor and local politicians led to those plans being revised. The US Army would build an airfield at the North of Castle Harbour. The US Navy would build a flying boat station at the West End. The US Navy began initial operation of Anti-submarine patrols by floatplanes operating from the Royal Air Force station on Darrell's Island. Its own base opened in 1941 as the Naval Operating Base, but was initially a construction site.
Two islands at the western side of the Great Sound, Tucker's and Morgan's, were levelled, adding 36 acres (150,000 m2) to Bermuda's landmass, and creating a peninsula extending from the Main Island. The entire base measured 260 acres (1.1 km2). It was not long enough to allow a useful runway, but did have extensive tarmac and hangar areas. Large Martin flying boats could be pulled ashore for hangarage, and servicing. When the area was first occupied by the US Navy, it was titled the Naval Operating Base. Once the Naval Air Station was completed, the US Navy relocated its air operations to it from Darrell's Island. The base continued to be used for this purpose until 1965, when the last flying boats were withdrawn from service. US Navy P-2 Neptune landplanes, based at the USAF base, Kindley Field, then took over the maritime patrol role. The US Navy took over Kindley Field, entirely, in 1970, and it renamed it NAS Bermuda. The former Naval Air Station was redubbed the NAS Annex. It served primarily as a dock area for US Naval shipping, until the closure of all of the US bases at the end of the Cold War, in 1995.
The military base, being self-contained and obeying the laws of its home county, had been very detached from the rest of the island. Without feeling a strong connection to Bermuda, and knowing that their presence was only temporary, the full costs of disposing of sewage and waste fuel on the base was likely never calculated. A 2002 report by the Department of Environmental Protection of the Ministry of the Environment estimated that 520,000 gallons of oil and several tons of raw sewage had been pumped into Bassett's Cave on the former NAS Annex, and a further 55,000 gallons of jet fuel pumped underground 200 ft (61 m) away.
In the decade since the pollution was discovered it has been left almost totally undisturbed. The base is very rarely opened to the public, and all talk of developing the lands has been stonewalled by the Government. The cave formation has kept the oil somewhat contained and the now abandoned base has not been opened to development for fear that the pollution may spread and have catastrophic costs. In order for one to properly analyze the situation, these costs must be well understood.