 In 1991 , the Navy discovered nine metals , two semi @-@ volatile organic compounds and a polychlorinated biphenyl in Ford Island 's soil , groundwater and marine sediment . Suspected sources were nine 225 @,@ 000 @-@ US @-@ gallon ( 850 @,@ 000 l ; 187 @,@ 000 imp gal ) fuel tanks on the east @-@ central side of the island ( from 1924 to 1954 ) , a 4 @.@ 4 @-@ acre ( 1 @.@ 8 ha ) landfill on the southwestern shore ( from 1930 to 1960 ) and ordnance bunkers on the northeastern side . An investigation suggested covering the contaminated areas with clean soil . In 1994 , the Navy considered removing the contaminated soil and installed six wells to monitor groundwater , but decided to follow the original recommendation in 1995 and capped the contaminated soil with topsoil and erosion @-@ resistant vegetation ( including Bermuda grass ) . The containment system was completed in 1996 . 
