Background: Fitted with integrated electrical auxiliary propulsion, the delivery of USNS Patuxent (T-ATF 201), USNS Rappahannock (T-ATF 204) and USNS Laramie (T-ATF 203) was delayed by the decision to fit double hulls to meet the requirements of the Oil Pollution Act of 1990. This modification increased construction time from 32 to 42 months and reduced cargo capacity by 17 percent, although this can be restored in an emergency. Hull separation is 1.83 m at the sides and 1.98 m on the bottom. USNS Henry J. Kaiser (T-AO 187) has become part of the MSC Prepositioning Program at Diego Garcia, carrying aviation fuel.