MOSCOW, September 11. / TASS /. The reason for the destruction of the fifth fuel tank at CHPP-3, the accident at which at the end of May entailed the largest ecological disaster in the Arctic, was a violation of technology during its construction about 40 years ago, the first vice-president and operating director of the company Sergei Dyachenko told reporters on Friday.

The construction of the reservoir took place in 1981. According to the building standards in force at that time, in the permafrost zone, the piles under the reservoir were to be deepened into the rock by 800 mm. However, during the dismantling of the destroyed storage facility, it turned out that this had not been done initially.

"According to our estimates, the distance from the bottom of the pile to the rock foundation is about one meter. So while this indirectly indicates that the piles were not completed according to the project, they were not buried in the rock," he said. According to the results of the core sample, between the piles and the rock of the reservoir, there was a soil consisting of sand and clay.

Most likely, about 40 years ago, the soil near the rock was severely frozen, Dyachenko admits. Therefore, they did not deepen the piles into the rock. The melting of permafrost has not manifested itself on the surface for decades. "The extremely warm summers over the past years and mild winters have made themselves felt, most likely. And the fact that colleagues once left these piles unburied played a cruel joke on us," he said. According to Dyachenko, it is still necessary to wait for the conclusion of the Investigative Committee, which is studying this issue.

Dyachenko also commented on the issue of the pre-emergency state of the fuel tank. "Indeed, in 2016 this tank did not pass the technical expertise, it was stopped. And I would like to say that in 2017-2018 it was under repair. After that, all the necessary state examinations were carried out, it was concluded that the tank suitable for use," he said.

Earlier, Rosprirodnadzor estimated the amount that got into Lake Pyasino and the Ambarnaya River at 15,000 tonnes. At the same time, about 6,000 tonnes got into the soil, the department said. In total, it was believed that about 21,000 tonnes flowed from the reservoir. According to Dyachenko, the volume of oil products that got into the soil has yet to be assessed.

In total, 188,000 tonnes of contaminated soil were removed, now it is stored in special hangars, said Dyachenko.

Speaking about the amount of damage in 148 bln rubles, which was previously announced by Rosprirodnadzor, Dyachenko said that "its clearly not like that." He also said that the company spent about 8 bln rubles in total to eliminate the consequences of the accident.

A claim to the Arbitration Court of the Krasnoyarsk Region against a subsidiary of Norilsk Nickel was filed by the territorial office Rosprirodnadzor. The court must decide on the acceptance of the statement of claim before September 15. According to official data, on May 29, more than 21,000 tonnes of fuel spilled after a storage tank collapsed at a power plant operated by CHPP-3, a subsidiary of metals giant Norilsk Nickel, in the city of Norilsk. The fuel leaked, flooding an area of 180,000 square meters of terrain and also into local rivers, causing damage to the environment.