Prior to the attack on Pearl Harbor all of the Navy’s fuel was stored in unprotected above ground tanks at Pearl Harbor, next to the submarine base.
When RADM Chester Nimitz was Commander of the Bureau of Yards & Docks (in 1940) he wanted the Navy’s 2 ½-year supply of fuel oil protected from aerial attack – existing aboveground unprotected tanks next to the Submarine Base presented a vulnerable enemy target.
In 1942, US victory at the battle of Midway altered the role of Hawaii from a defense position to “a springboard for the Pacific offensive. Troops poured into the islands en route to the western Pacific, and were housed in barracks and makeshift camps throughout the islands.”
“There were 43,000-soldiers on Oʻahu on December 7, 1941, plus a handful on the other islands. In the first six months of the war, the total swelled to 135,000. By June of 1945, when plans were mounting for an offensive against the homeland of Japan, troops on Oʻahu alone numbered 253,000.” (Allen; army-mil)
Jungle training and coordinated Army-Navy amphibious landings were practiced in anticipation of the island-hopping battle strategy of the western Pacific. Areas on Oahu that had been taken over by the military at the onset of war were developed as training areas.
“Hawaiʻi served as an invaluable training ground for the amphibious and jungle warfare which characterized the Pacific fighting. Well removed from the combat zone, yet 2,000 miles nearer the battlefront than the Mainland …”
“… there was sufficient area and enough equipment in the Islands to handle many thousands of troops and to embark them for large-scale operations. More important, some of the varied climates and terrains in Hawaii were like those of the target areas.” (Allen; army-mil)
To fuel the forces, the military had three major fuel storage sites located in the mauka lands of Oʻahu: Red Hill Underground Fuel Storage Facility, Waikakalaua Fuel Storage Annex and Kipapa Gulch Fuel Storage Annex (other storage areas supplemented the effort.)
The Red Hill Underground Fuel Storage Facility was started the day after Christmas 1940 and continued through 1943; 20-underground fuel storage tanks were built more that 100-feet below the surface. The facility was designed as an impenetrable, bombproof reserve of fuel for the military.
Each vertical tank is 100-feet in diameter and 250-feet high, roughly the size of a 20-story building, and lined with quarter-inch steel plates.
Each tank is able to store up to 12.5 million gallons of fuel. it has an overall design capacity of 6-million barrels of fuel oil (9.97-billion gallons.)
Dug from the inside, the storage facility is connected with pipes (32-inch-diameter diesel pipe, and 18- and 16-inch jet fuel pipes) and tunnels down to a Pearl Harbor pumping station, more than two-and-a-half miles away.
The tanks were set up in two parallel rows with two main access tunnels, one above the other, bisecting the rows; smaller tunnels branched from these main axis tunnels to the tank cavities.
Waikakalaua Fuel Storage Annex near Wheeler Army Airfield, one of two Air Force Fuel Storage Annexes, was made up of nine 1.75-million-gallon underground storage tanks.
It borders the Wheeler Army Airfield on the Schofield Plateau; underground fuel storage tanks are reported to have been constructed between 1942 and 1945, and were used to store various fuels since 1943.
The other Air Force fuel storage facility was the Kipapa Gulch Fuel Storage Annex that consisted on four massive underground tanks. Each tank is three times the length of a football field. Each tank could hold 2.4-million-gallons of fuel.
A 20-mile, 10-inch pipeline connected the Waikakalaua Fuel Storage Annex and the Kipapa Gulch Fuel Storage Annex with Hickam Air Force Base. Fuels that were stored in the tanks included aviation and motor gasoline and later, JP-4 and JP-8 jet fuel. (army-mil)
The image shows the aboveground fuel storage tanks at the Submarine Base in Pearl Harbor. (October 13, 1941)