1991 - Alessandro Primo

On February 1, 1991 at 11.15am, the M/T "Alessandro Primo", of Italian flag, owned by Trasporti Marittimi, sunk approximately 16 nautical miles off Molfetta, NE Italy. By 12.00am, all the crew were rescued by helicopter.

Acrylonitrile is toxic in both liquid and vapour and can be lethal in high concentrations. It has also been found to be carcinogenic over long exposure periods. However, no permanent damage is considered to be caused by short-term exposures once a person recovers from the acute exposure.

Because of acrylonitrile's tendency for polymerising during transport and storage, an inhibiting agent is added to the liquid which temporarily prevents this reaction. If uninhibited, runaway polymerisation occurs and the heat liberated during the process may cause the chemical to explode, particularly if the liquid is contained.

If spilled into the marine environment, acrylonitrile will dissolve and evaporate.

Dichloroethane is a flammable liquid. Combustion products include hydrogen chloride and phosgene. Its vapours are heavier than air and can cause dizziness. Its vapours may also be poisonous if inhaled. Contact with skin or eyes can cause irritation or burn the skin. If spilled into the environment, the product will sink and dissolve.

On February 1, 1991 at 11.15am, the M/T "Alessandro Primo", of Italian flag, owned by Trasporti Marittimi, sunk approximately 16 nautical miles off Molfetta, NE Italy. By 12.00am, all the crew were rescued by helicopter.

Acrylonitrile is toxic in both liquid and vapour and can be lethal in high concentrations. It has also been found to be carcinogenic over long exposure periods. However, no permanent damage is considered to be caused by short-term exposures once a person recovers from the acute exposure.

Because of acrylonitrile's tendency for polymerising during transport and storage, an inhibiting agent is added to the liquid which temporarily prevents this reaction. If uninhibited, runaway polymerisation occurs and the heat liberated during the process may cause the chemical to explode, particularly if the liquid is contained.

If spilled into the marine environment, acrylonitrile will dissolve and evaporate.

Dichloroethane is a flammable liquid. Combustion products include hydrogen chloride and phosgene. Its vapours are heavier than air and can cause dizziness. Its vapours may also be poisonous if inhaled. Contact with skin or eyes can cause irritation or burn the skin. If spilled into the environment, the product will sink and dissolve.

Following the SAR operations, the Harbour Master at the Molfetta harbour evaluated the impact on the environment and the following decisions were made:

a) a state of emergency was declared;

b) a technical-consulting committee was established;

c) navigation and fishing were banned in a radius of 10 miles from the point of sinking;

d) a wider area was patrolled by air and sea with instructions given to report any unusual sightings, such as fish kills, abnormal presence of sea birds, iridescence, etc.;

e) observations were to be carried out by a remote operated vehicle to locate the wreck;

f) the ship owner was ordered to remove the cargo to prevent possible pollution.

The position of the wreck was determined with some difficulty. It was located at a depth of 108 metres with the bow completely buried in the mud. The wreck's stern sat clear off the bottom with the rudder and propellers visible. Moreover, the presence of large amounts of mud on the front part and the angle of over 30 degrees with the bottom indicated how the vessel had gone under and it was estimated that the speed with which the ship went down was around 7m/sec (Figure 1).

Video footage from the ROV showed that product was leaking from a coupling flange in the cargo line of the top of tank 5 containing acrylonitrile. Confirmation that this was acrylonitrile came from observations of dissolution of paint work from the piping on the wreck, as well as an upward movement of the product towards the water surface (acrylonitrile is less dense than water).

Water samples were taken around the wreck and only on February 5 were appreciable traces of acrylonitrile detected (2.7ppm).

It was necessary to plug or reduce the rate of loss which was to be done by divers, whilst consideration was given to recovering the products in the tanks. The possibility of recovering the wreck intact was excluded since the hull was structurally compromised.

Plugging of the leak was to be done by divers, however consideration was given to:

1) the depth of the water in which the divers were to work; and
2) the toxic nature of the product and the solvent event of the acrylonitrile on the material of construction of the divers' equipment, e.g. rubber suits.

Due to these problems and the absence of toxicological values (e.g. TLVs) for environments containing helium-oxygen mixtures, it was decided that a zero safety threshold be set to protect the health of the divers. This made it necessary to impose rigorous procedures for the transfer of the divers from the diving to the decompression chamber.

The leakage of acrylonitrile was halted by applying special sealing caps to the air outlets relative to the valves of tank 5 to reduce the water entry and using special epoxy resins on the flanges. This operation was completed on February 21.

Following sealing, attention was focused on the recovery of the products from the wreck. A salvage operation of the ship and its cargo was not possible due to the poor state of the vessel. The empty wing tanks had imploded (inward explosion) due to water pressure. Further consideration was given to the fact that each product recovered and any tank washing were to be kept separated to ensure that the recovered products could be regenerated and reused.

The operation for recovery had to be organized in such a way to ensure:

1) maximum protection to the underwater and surface operators;
2) that the products and washing water were transferred in the shortest time possible;
3) continuous monitoring of the surrounding sea water;
4) safe moorings on the sea bottom at 108 metres depth up to the vessels used in the operations;
5) a rapid system for personnel evacuation in case of sudden spillage of acrylonitrile following the structural collapse of tank 5.

A contract was awarded as a joint venture to Smit Tak and two Italian companies, Technospamec, saturation diving specialists, and the shipping group Diamar. The contract was awarded by the Italian authorities on April 29 which called for the removal of all cargo.

The Diamar diving support vessel Ravello acted as a base for a team of 20 Technospamec divers, whilst the marine survey ship Mare Oceanio served as accommodation and had a hellideck for use in medical evacuation. Other units on site included a 90 x 30 metre barge outfitted as a floating pumping station.

On April 5, preliminary operations for recovery began. Sampling showed that cargo was only present in the centre tanks (see Figure 2). The transfer system was set up which essentially consisted of one or more hydrodynamic immersed pumps with a variable capacity of 40/60 m³/h and a series of 3 inch metallic hoses compatible for handling the product.

To reduce the dead time of transfer from one tank to another, the immersed pumps were connected to an underwater floating manifold which fed into a floating pumping station equipped with a series of five pipes which drew from individual tanks which in turn fed into the lightering vessel (see Figure 3).

The principal behind this concept was that, in case of emergency or bad weather, divers could easily disconnect the cargo pumps and the hydraulic hoses with the rest of the system still in place not affected by waves.

During the course of operations, fire fighting vessels were positioned in case of a sudden release of acrylonitrile and were prepared to knock down any vapour clouds with foam. A medical station was set up, whilst a helicopter was put on standby.

Of the two products, acrylonitrile was considered to be more toxic and more easily dispersed in the marine environment. It was therefore given priority. The pumpout began on April 22 and was completed over a period of seven days. The two products were pumped into two different tankers. It took just over one day to complete the pumpout for acrylonitrile. In the
pumpout, approximately 900 cubic metres of acrylonitrile mixed with water was recovered. The low acrylonitrile content in the product-water mix did not allow recovery of the product. On April 23, pumpout of dichloroethane began. The operation ended on May 1. The amounts recovered were 2,182 cubic metres of dichloroethane and 2,850 cubic metres of tank washing. The high concentration of dichloroethane permitted its recycling. All washings were treated according to the national environmental procedures.