The marine ecosystems of Aniva Bay and the north-eastern shelf of Sakhalin Island are characterised by rich biodiversity combined with high environmental sensitivity. These water areas are important for fisheries and belong to the highest fishery category. They are inhabited by more than 100 species of valuable commercial fish (including salmon, herring, cod, and flounder) and invertebrates (certain species of crab, shrimp, and gastropods). These water areas are also important habitats for rare and protected species of birds and marine mammals.

Man-made impact on ecosystems may cause damage to marine biological resources. This is the reason why environmental safety, protection, and preservation of the vulnerable marine environment and biota is a priority for Sakhalin Energy LLC in its activities offshore Sakhalin.

There are potential environmental risks stemming from a combination of difficult natural and climatic conditions of offshore field development, the ecological vulnerability of northern ecosystems, and the occurrence of valuable commercial and rare species of marine hydrobionts.

These factors require timely assessment and environmental risk management during the Company's operations. To prevent and minimise negative environmental impact, regular environmental monitoring is carried out in line with the environmental legislation of the Russian Federation as well as corporate standards, which include international best practices and technologies.

Environmental monitoring program for offshore production facilities 

Sakhalin Energy LLC performs environmental monitoring within the water area of the oil and gas field license areas and Prigorodnoye port at the operation stage. The monitoring is performed to identify the potential environmental impact of the Company's operations in a timely manner and to forecast the development of processes that affect the quality of the seawater, bottom sediments, and biological communities, as well as to make decisions regarding environmental impact control and develop corrective measures.

As part of industrial environmental monitoring in zones of potential impact by offshore assets, the Company checks the condition and interannual variability of marine environment and biota parameters in the following areas:
• PA-A, PA-B, and LUN-A fixed production platforms,
• subsurface drilling waste disposal facilities at the Piltun-Astokhskoye and Lunskoye oil and gas fields, and
• LNG jetty and the tanker loading unit of the oil export terminal (TLU-OET) of the Prigorodnoye production complex, Aniva Bay.

The monitoring programme includes checks on hydrological measurements, hydrochemical analysis, the presence of pollutants in seawater, and the physico-chemical composition of bottom sediments, as well as observations of planktonic communities and benthos. With these data, it is possible to characterise the marine environment when evaluating man-made impacts.

Since 2018, field surveys in the areas of oil and gas fields have been conducted from offshore standby vessels. The marine environment in Prigorodnoye port (Aniva Bay) is monitored from the Company's tugs or a standby vessel, which allows for reliable organisation and optimisation of the work scope.

The spatio-temporal variability of environmental parameters is assessed based on the analysis of long-term monitoring data versus background values and established standards, which leads to the following conclusions:
• Hydrochemical indicators and levels of contaminants in the seawater near the Sakhalin-2 offshore assets correspond to the maximum permissible concentration (MPCf) values established for fishery waters and fall within the range of baseline values for these water areas.
• The content of contaminants in the bottom sediments near the Prigorodnoye license areas and offshore assets varies within the range of baseline values for these water areas and is below the limit of concentrations causing initial biological effects at the level of organisms and communities of marine ecosystems. Concentrations are distributed unevenly due to the mosaic spread of various soil types and regional geological features of the monitored areas.
• Benthos communities in the zones of potential impact of the offshore platforms and Prigorodnoye assets are typical for Sakhalin shelf waters. They are characterised by rich species diversity and high quantitative indicators comparable to the baseline values. The identified communities are variable in composition depending on water depth and types of bottom sediments. The community structure is stable, with no trends towards a decrease in the biomass or the number of organisms, which confirms a lack of impact from the Company's operations.

The findings of long-term studies indicate that the local marine ecosystems near Sakhalin Energy's offshore assets remain stable during the operation stage. This lack of impact by the Company's assets on the quality of marine waters, bottom sediments, and marine biota in the water areas of the Piltun-Astokhskoye and Lunskoye fields on the north-eastern shelf of Sakhalin and Prigorodnoye Production Complex in Aniva Bay confirms that the Company is fully compliant with standards and baseline values.

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