A standby underwater leg was started to be laid on an important section of the oil trunk pipeline.
The Far East subsidiary of Transneft has set to laying a standby leg of the underwater crossing within the second phase of the Eastern Siberia – Pacific Ocean (ESPO-2) pipeline system via Tunguska, a left-bank tributary of the Amur River. This will make the operation of the oil trunk line even safer and more reliable after its capacity has been increased to 50 MTPA.
The width of Tunguska in the area of the underwater crossing is only 156 metres, whereas the length of the standby leg will reach 17 km including the stream bed
The new leg of the underwater crossing will pass through bogged stream beds which are fully or partially inundated in times of flood in parallel with the main one. The length of the standby leg will be 17 km of which only 460 metres will be laid over the river waters. The work will be carried out in the territory of Jewish Autonomous Region and Khabarovsk Territory, Tunguska being the administrative border dividing these two regions. The construction is scheduled for completion by autumn 2021.
Now crews are getting the site ready clearing the corridors, placing essential machinery and starting the welding of qualification joints. Engineering surveys and design had lasted one year and a half prior to the beginning of construction works.
Why standby legs of underwater crossings? Several water arteries stand in the way of ESPO-2, including some major rivers such as Amur, Ussuri, Zeya, Bureya. In these cases, pipes are laid underwater, with 52 underwater crossings located in the area of responsibility of Transneft Far East. Highest requirements are laid upon the reliability of these sections: here even the slightest damage is inadmissible, since the matter regards the environmental safety of the river.
Pipeliners are very serious about building and operation of underwater crossings. A standby leg of the ESPO-2 crossing over Amur was commissioned in 2019; the construction of six more is scheduled for 2020-2024: over the Tunguska, Khor, Zeya, Bureya, Bolshaya Ussurka and Ussuri Rivers.
Laying an oil pipeline leg is more than just placing a pipe underwater. A great bulk of preliminary works was completed in the course of building the main leg of the crossing over Tunguska. To ensure an all-season access to the pipe, specialists laid a route road to the entire extension of this section back in 2015-2016. A lot is yet to be done ashore: building an access road, fiber-optic communication line, as well as a multitude of other facilities.
Yet underwater works call for a special approach. Specialists decided to perform them in winter during the season of sustainable negative temperatures.
“The designers tapped into the experience of building the main leg of the underwater crossing over Tunguska,” says Deputy Director General for Construction at Transneft Far East Evgeny Sukhushin. “The project was implemented as part of the second phase of ESPO-2 during the spring-summer season. We took into consideration all unforeseen difficulties encountered by builders of the main leg, changing the method and period of works.”
According to Mr. Sukhushin, strict control of construction works will be put in place - from additional geodesic and visual monitoring of the aboveground trench to industrial radiography of absolutely all welding joints. This will assure both the quality of construction and its environmental safety. A specialised entity will check the keeping of all eco standards. The sphere of its responsibility includes the monitoring of atmospheric air, industrial emissions, chemical composition of groundwaters, topsoil and bottom sediments. Monitoring the river condition with sampling, the condition of water protection zones along with fauna and flora is also a must. Certain restrictions are inevitable – e.g. they will pertain to the works done during the spawning period. After the building works are complete the topsoil will be reset and normalised.