E.А. Rybak1,2, Y.I. Yurenko2
1Branch of Institute of Natural and Technical Systems, RF, Sochi, Kurortny Av., 99/18
2FRC SSC RAS, RF, Sochi, Theatralnaya, 8a
Currently, several tens of subsea pipelines are in operation on the Black Sea coast of the Caucasus – sea water intakes and wastewater outlets. Wastewater outlets are divided into shallow water (up to 5 m), deep water (up to 10 m) and abyssal water (over 25 m) outlets depending on the depth of the outlet head location. Shallow water outlets are used to drain rain waters into the sea, while deep and abyssal water outlets are designed to dump purified wastewater from sewage purification plants. Most of the existing subsea pipelines were built in the 60s-80s of the 20th century and are now physically significantly worn out, partially destroyed or simply decommissioned.
The pollution of the marine environment off the Black Sea coast of the Caucasus with household wastewater poses a serious threat to the local population and numerous tourists. Periodic dumping of unpurified wastewater and pipeline accidents require regular monitoring of the coastal waters. At the same time, it is possible to significantly reduce the risk of accidents on pipelines already at the design stage. In particular, a brief analysis of the natural conditions of the Russian shelf of the Black Sea coast of the Caucasus and the accident rate of subsea pipelines makes it possible to recommend the use of steel pipes in the construction of communal systems of marine water supply and sewerage. The use of plastic pipes is permissible only at depths of more than 25 m. In the upper shelf zone, the construction of completely plastic submarine pipelines is reasonable only if they are properly buried in the layer of loose bottom sediments or in the bedrock of the bench. Additionally, we can recommend application of measures to compensate for linear temperature deformations of the pipes.
Keywords: underwater pipeline, deep-sea release, sewage treatment plant, temperature stratification, shelf, bottom sediments.
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