1. Initial Responses to the incident of the NAKHODKA
A massive oil spill, which was caused by the fracturing of the hull of the Russian tanker NAKHODKA (gross tonnage: 13,175 t) occurred at about 0250 hours on 2 January, 1997, was first identified together with the sheared-off bow section on the Japan Sea by an aircraft and a patrol boat of the Maritime Safety Agency on the following day, 3 January. A large amount of oil spilling from the sheared-off bow section of the wreck and oil slicks drifting in the vicinity were verified during this first discovery.
A salvage boat dispatched at the request of the shipowner for rescue operations arrived at the scene of the incident at 2130 hours on 4 January, and tried to tow the bow section, which was then drifting, with assistance provided by the patrol boat. The drifting bow in the bottom-up position, exposing only a small portion above the water, coupled with the heavy seas prevented them from belaying towing hawsers.
On the morning of 5 January, the head of the spilled oil drifting together with the bow had already approached a point 40 nautical miles off Mikunicho. The oil pushed by northerly winds was likely to menace the coast of Japan.
The patrol boat and other vessels began to remove drifting oil, while making an attempt to tow the bow. At the initial stages, recovery nets were used to recover the oil, oil dispersant were sprayed onto the sea, and on 5 January, a helicopter was tested for spraying oil dispersant.
2. Off-shore Drifting and On-shore Conditions of Oil
It was estimated that about 3,700 kL, contained in the bow section, of about 19,000 kL of C heavy oil that the NAHKODKA carried had instantaneously been discharged into the sea through fractures following the hull damage. (The investigation performed afterwards made us estimate the oil spill to be 6,240 kL.)
The oil slick drifting on the sea surface were broken up in places by waves but thick layers of the principal part and the bow pushed by the currents and northern seasonal winds were approaching the coast of Honshu, Japan.
The drifting bow reached a point off Anto Misaki. Mikunicho. Fukui Prefecture at about 1100 hours on 7 January, while rough weather continued dominating the waters of the Japan Sea. Another oil spill from the bow was identified. All these oil slicks reached and landed on the neighbouring coasts.
On 8 January, diffusing layers of oil came ashore consecutively on the coasts of Fukui Prefecture and Ishikawa Prefecture.On 20 January, the oil layers drifting northwards along the Noto Peninsula finally passed the northern coasts of the Peninsula and were driven to Sado Island, Niigata Prefecture, eventually reaching other coasts of Niigata Prefecture on the Honshu side. As a result, contamination of waters was found to be affecting 9 prefectures including Shimane and Akita.
3. Oil Recovery Operations
All oil recovery operations included recovery of oil drifting on the sea, recovery of oil drifting near the coast and recovery of oil driven onshore and dwelling on sandy shoals and rocky beaches.
(1) Recovery of oil drifting on the sea
The spilled oil was driven onto the long coastline from Shimane Prefecture to Akita Prefecture. Part of the oil took a northern course off from Wakasa Bay and along the coast of Fukui Prefecture and Ishikawa Prefecture and reached the coast at the northern end of Noto Peninsula, Toyama Prefecture and Niigata Prefecture, widely diffusing on the sea.
When more than one week had passed since 2 January, the date the incident occurred, the spilled oil which had been continuously stirred by waves since then became a emulsified oil containing a large amount of water. According to data, the properties of the oil carried by the tanker, which was loaded in Shanghai, are: kinetic viscosity: 137.46 cSt at 50℃ (about 6,000 cSt at 10℃) ; pour point: -17℃. The drifting oil sampled on 5 January presented a viscosity of 1,232,000 cSt at 12℃.
a) Crane barges and grab dredgers
It was foreseen that such high-viscosity oil could be recovered more effectively by means of crane barges and grab dredgers than by oil recovery systems. Such vessels were chartered and used for oil recovery operations at sea.
