The question is not so farfetched as you may assume. The M/S Estonia had two sewage collection tanks located on deck 0 inside a watertight compartment on starboard side served by two watertight doors, one forward and one aft and with a stairwell leading up to deck 1 above. In a cabin (marked yellow) on deck 1 just above the sewage tank compartment resided the survivor CÖ, who heard two sharp bangs just before the ship lost its initial stability at about 01.02 hrs and heeled to starboard. CÖ also noted that water shot out from some mysterious air pipes with swan necks ending on deck 1 above the sewage tanks before the ship listed. These swan necks may have been connected to the tanks in one way or another. CÖ run up from his cabin (marked yellow below) following the green path to the stairwell.
We have also been told that systems engineer Henrik Sillaste had been called upon at 00.30 hrs to fix a problem with the sewage system - lost vacuum. So what could have happened?
Sewage tanks and systems are famous for corrosive attacks. The black water being biologically treated and injected with air is quite acidic. The sewage tanks and pipes are therefore internally protected by epoxy, but it is well known that the epoxy protection breaks down and that the bare steel corrodes quickly. There are numerous examples that sewage tanks leak on ships due to internal corrosion and that the relevant compartment is flooded by - shit. Cacca in Italian! Quite a mess. Heiwa Co has repaired several corroded sewage tanks on passenger ships and ferries in the past. Dirty business.
Let's assume that the sewage tanks of the 'Estonia' were in a bad condition and that a big internal leak occurred at the night of the accident and that the sewage tank compartment tank top was flooded with shit! Naturally the vacuum of the system dropped - and this was reported to have happened - at 00.30 hrs. Sillaste was called upon to help Treu and Kadak to sort out the mess. The first action would have been to start a bilge pump and pump the shit overboard and Sillaste has told that the bilge pumps had been started. The location of the sewage tank compartment on deck 0 is shown on this Plan of decks 0 and 1.
The sewage tank system evidently had an overboard discharge and maybe a sea inlet, i.e. it was connected overboard via sea valves. Here something may have gone wrong, because there must have been a serious hull leak to sink the ship. I assume that a sea valve must have collapsed and that a serious leak started - the whole sewage compartment started to fill up with sea water! It could have been so simple that the sea valve was blocked - it could not be opened - and that Sillaste and Treu tried to open it with a sledge hammer - and that the whole thing came lose. Some survivors are stated to have heard some sledge hammer bangs - and it has been assumed that the crew tried to activate the starboard stabilizer. I assume further that Sillaste and Treu at this moment closed the two watertight doors to the compartment and retreated to, e.g. the Engine Control Room on deck 1 and reported to the bridge. The situation was then under control - the ship would survive one-compartment flooding and the bilge pump was running trying to keep the sea water out.
Things go wrong
But then matters went wrong. The inflow into the sewage compartment was massive - a 0.2 m2 opening in the hull - 50-100 m3 inflow per minute and the bilge pumps could not keep up. And then somebody must have opened the watertight doors from the control panel on the bridge. The result was the 'Estonia' disaster. Two big bangs followed - CÖ heard them - when the two watertight doors under pressure were opened. Water spread on the tank top in three, four compartments of the hull - loss of stability resulting in >30 degrees list followed at 01.02-01.05 hrs. Treu, Sillaste and Kadak fled to the open deck.
But the ship then uprighted and was stable with 15 degrees starboard list for some time. The ship would in fact not have listed >21 degrees with water only on deck 0. More water leaking in on deck 0 should have made the ship more stable during the sinking and made it more upright. Why did the ship list more and more, so that she was on the side - 90 degrees list - at 01.30 hrs? One possibility is that either the starboard pilot door or the starboard bunker port leading into the superstructure was not properly secured and that water spilled in on the car no. 2 deck that way. The contribution of stability when heeling by the superstructure above the waterline was then impaired, so the ship could list 90 degrees - without capsizing and sink at 01.36 hours.
Why the Joint Accident Investigation Commission later 1994-1997 tried to blame the whole accident on the visor and water inside the superstructure is another stupid story. The Commission could not believe that the 'Estonia' sank due to a stupid fault of the sewage system followed by very negligent handling of the watertight hull doors by the crew? Of course, the 'Estonia' lifesaving equipment was rubbish since 1980 and there were many other defects to hide. The ship was not seaworthy! Or maybe the JAIC believed that the ship had been sabotaged by a third party and tried to hide that for political reasons? Or, later, it became known that the ship was used to carry ex-USSR military equipment to Sweden and it was maybe sabotaged.
In March 2003 the Swedish Board of Psychological Defence published a Pre-Study about how the Estonia was filled with water and sank 1994. The Pre-study contains an amazing amount of false information. Read the Pre-study!
Published 3 March 2002.