2.6. Cleanup of the Bay of Tiksi Seafloor from Sunken Logs and Shipwrecks Pilot Project

The Project Goal was to protect the biosphere in the marine and coastal zone of the Bay of Tiksi and Gulf of Bulunkan from man-induced pollution. The Project was to cleanup the coastal zone of the Bay of Tiksi and Gulf of Bulunkan from sunken timber and to prepare 5 sunken vessels for salvaging. 

The Project was implemented by Open Joint Stock Company “Tiksi Sea Port”. The Project also contracted the Federal State Organization "The State Nature Reserve Ust’ - Lensky" to do the pre-cleanup and post cleanup assessment of the pollution levels of the Bay of Tiksi analysis of the environmental status of the Bay of Tiksi and the Gulf of Bulunkan.

The Project Duration:           01 July 2008 - 08 August 2009;

The Project Activities

1. The Project analyzed the existing domestic and foreign practice in the water area cleanup operations, prepared the design documentation, and trained the Port technical personnel in the safety and quality of the cleanup operations in the bay. The Project also carried out the depreservation, repair and restoration works on small vessels, lifting equipment and small tools and equipment. The Project assessed the pre-cleanup pollution levels in the Bay of Tiksi.     
2. The seafloor of the Gulf of Bulunkan was dredged with a grappler installed on the floating crane to lift the sunken logs, load them onto a pontoon or seaborne barge, and transport the logs to the onshore offloading point to be graded and banked.
   
   

   
   Figure 15. Salvaging Timber from Tiksi Bay Seafloor

3. The preparatory work on the hulls of the wrecks was carried out including: (i) diving survey; (ii) for salvaging purposes, work was done to fix damaged areas of the sunken vessel hulls by establishing five water-tight patches; (iii) a methodology for lifting the wrecks was identified and approved.
   

   
   Figure 16. Shipwrecks in Tiksi Bay

4. One more study of the water quality in the Bay of Tiksi and the Gulf of Bulunkan was carried out. Following this, a comparative analysis of the water contamination before and after the cleanup, as well as assessment of the environmental status of the bay waters was carried out.

The Main Outcomes

Prior to the cleanup of the seafloor in the Gulf of Bulunkan (1 August 2008), the Project carried out hydrobiological monitoring of the zooplankton and zoobenthos in the waters of Bay of Tiksi and the Gulf of Bulunkan. The water pollution levels (water quality based on hydrobiological indicators) was assessed through the use of the Goodnight - Wheatley index and Woodywiss F. Biotic index for water zooplankton and zoobenthos and the oligohet ratio to the overall number of zoobenthos organisms.

The long-term monitoring showed that the Gulf of Bulunkan as compared to the Bay of Tiksi is characterized by lower values of abundance, biomass and species composition of zooplankton (9 species versus 20). This is due to man-induced pollution, low oxygen content in winter and high levels of sulphides and chlorides. The species composition of blue-green and green algae is poor, dominated by diotom species of algae. The scientific study of the samples of zooplankton and zoobenthos showed that water is of moderate contamination.  The water saprobity class was defined as mezasaprobity, i.e. there is pollution.

Environmental degradation in the shallow waters of the Gulf of Bulunkan as compared to the Bay of Tiksi was caused by a combination of various detrimental factors. The biggest contribution to the water pollution is phenols accumulating from rotting sunken logs and wood residues. According to the characteristics of the bottom-dwelling biocommunity obtained during monitoring (August to October), all the Gulf samples showed that water  (water purity grade) was moderately polluted, while water in the Bay of Tiksi was clean. In other words, the quality of water in the Gulf of Bulunkan was worse than water quality in the open water area of the Bay.

Entering the coastal waters, pollutants have a repelling impact on fish and change the conditions of fish feeding, wintering and spawning. They also contribute to high concentrations of fish shoals within a limited area, while keeping the fish from the fodder organisms, making it difficult to use the feeding resources and reducing the biological productivity of the water body as a whole.  

Direct poisoning of water with toxic pollutants and industrial waste, reduced aeration of the water body due to the freezing up or man-induced contamination with oxidizing organic pollutants, in particular caused by the accumulation of decaying vegetation, timber or development of toxic microorganisms may generate fish kill conditions or kill fish outright because of insufficient amount of oxygen in the water of the Gulf of Bulunkan. Water is especially oxygen-poor in winter, with ice cover growing thicker. The thicker the ice cap is the less the amount of water in the bay and this contributes to the concentration of organic, biogenic, and polluting substances in the bay. Also, the Lena River carries less fresh oxygen-rich water into the Bay of Tiksi and Gulf of Bulunkan. Decomposition and decaying of the sunken logs intensifies generation of pollutants and uptake of oxygen.

The purpose of the cleanup operations was to determine how strong will be the effect of the effort to trawl out the decaying timber in one season on the quality of the Bay water in future. The 2008 seafloor trawling was launched in the shore area of the southeastern part of the Bay. In 2009, trawling continued in the shore area 400 m wide, in the western part of the Bay up to the Cape of Ice (the works were completed on 8 August 2009).

The seafloor cleanup operations (the diagram is attached) were carried out in an area of over 500,000 m2 (0.56 km2). All in all, 41 shifts produced 1,900 m3 of logs lifted from the seafloor. Most of it (over 80%) was rotten, causing biological contamination of water, in particular with phenols. In addition, the cleanup operations lifted from the seafloor 22 tons of steel wire, wire ropes and chains taken onshore for recycling.

We may calculate accumulation of the decaying timber per square meter of the seafloor by dividing the amount of the timber lifted (1,900 m3) by the seafloor area cleaned up (560,000 m2) to receive 0.0034 m3/m2.

Thus, in order to lift 1 m3 of logs from the seafloor, it will be necessary to trawl about 300 m2 (294 m3 is an area of 20*15 m). This will require up to 100 cycles of the lift-lower movements of the clamshell. In other words, the seafloor cleanup operations were very intensive.

Upon the completion of the seafloor cleanup operation, the Project carried out another hydrobiological and hydrochemical analysis of the water samples taken at the site of the cleanup operation in the Gulf of Bulunkan, as well as at the site of the operations in the Bay of Tiksi. The comparative analysis against the 2008 initial studies showed improvement in the water quality demonstrated clearly by an overall increase in the density of communities and biomass of both zoobenthos and zooplankton. The analysis also found that after the cleanup the bay seafloor amount of pollutants, in particular phenols, was reduced due the reduction in the amount of decaying wood, the main source of phenols.

CONCLUSIONS

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