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Precis File
SHIP NAME: Sansinena KEY: NUM. ENTRIES: 4
source USCG
type D
volume
material
dead 9
link http://www.uscg.mil/hq/g-m/moa/boards/sansinena.pdf

Ship had finished discharging at Los Angeles and was ballasting. All P/V valves were in hand-opened position in part because had to release pressure to do survey. Wind from aft end at 8 kts, but ship had a midship house, and two ballast tanks next to house had been converted to crude. USCG thinks hydrocarbons built up in protected area around midship house, which had plenty of possible sources of ignition. Problem was exacerbated by many holes on underside of vent piping on deck.


source OSCH
type A
volume 30000B
material
dead 9
link

At 1938 on December 17, 1976, the Sansinena exploded, caught fire, and sank during refueling at the Union Oil Terminal, Berth 46, in Los Angeles Harbor, California. The vessel was loaded with 22,000 barrels of Bunker C at the time of the incident. The apparent cause was a still-air situation that developed between the mid-ship house and the afterdeck house. Vapors emitting from the cargo tank vents created a vapor cloud during ballasting. These were ignited in the midship house and flashed back through the vent piping system. The largest explosion took place in the number 10 center cargo tank. The force of the explosion propelled the main deck over the cargo tanks into the air. When the deck landed, it severed a 36-inch cargo line on top of the inshore isolation valve. This severed line fed fuel to the fire until response personnel discovered and capped it on December 21. Nine lives were lost as a result of the explosion. Debris and oil scattered in all directions. Approximately 400 boats in the vicinity were damaged by the fine mist of airborne oil, resulting in millions of dollars in property damage. An estimated 30,000 barrels of oil were released into Los Angeles harbor from the ship and the severed pipeline. A U.S. Coast Guard boat and a Los Angeles City Fire Department boat arrived on-scene within five minutes of the explosion to assist in firefighting and rescue operations. Pollution surveys were conducted after the fire was under control. Initial reports concluded that much of the oil had burned off, but on December 19, underwater divers discovered a large quantity of oil on the bottom of the harbor. The primary cleanup contractors were IT Corporation, Crowley Environmental Services, Crosby and Overton, Inc., and Fred Devine Diving and Salvage, Inc. Boom deployment began within two hours of the explosion. Boom and other containment gear were utilized for the next 120 days, while mechanical removal of oil from the bottom of the harbor continued for 16 months. Total oil removal costs exceeded three million dollars.


source ETC
type D
volume 23810B
material No 6 Bunkers/naptha
dead
link

OSIR puts spill at 1,385,000 gallons.


source CTX
type C
volume 30000B
material B
dead 9
link

Cargo had been very volatile Attaka Crude with a 7.9 psia RVP. Ship not inerted. All P/V valves and ullages covers open. This was ships SOP to avoid over-pressuring tank during ballasting. Ballasting pushed vapors on deck. 5W whose expansion trunks were under the midships house had been converted to cargo to take advantage of additional deadweight associated with 1966 regulations. Wind was light from the stern, allowing vapors to collect in protected area between houses. Vent trunk to machinery spaces in mid-ship house were on aft side of house above this area. Ship had a draft forward/aft of 12/26 ft, over 7 m of trim. Cargo tank vent piping had numerous holes on underside.

USCG thinks some of the vapor was pulled into the midship machinery space, ignited, deck between houses went up and then the tanks themselves. Given that everything was open doubt if the holes in the piping made much difference.

As a result of this explosion which cause a lot of damage and injuries on-shore, the USCG, 8 years after Mactra et al. belatedly decided to require inerting on all tankers above 20,000 tons trading to US ports. Not sure when this came into effect. The USCG had already required inerting on all tankers above 100,000 dwt (all combo carriers above 50,000 dwt) with keel-laying after Dec 31, 1974. As slow as this was, USCG was well ahead of IMO.

Requirements with respect to closed loading were much slower in coming.