The Red Hill facility is unique in that the 20 vertical cylindrical tanks, each measuring 77 m (250 feet) tall by 30 m (100 feet) in diameter, are hollowed out of volcanic rock, 30 m (100 feet) under a ridge within Honolulu, Hawaii. Red Hill construction occurred from 1940 through 1943, continuing at the time of the attack on Pearl Harbor on December 7, 1941. The facility is connected by pipes and tunnels to navy piers and other shore facilities more than 4 kilometres away. Red Hill was designated a historic civil engineering landmark by American Society of Civil Engineers.