REUTERS Natural gas stocks in Ukraine&#39;s underground storage facilities (USFs) have increased by 54%, to 13.475 billion cubic meters (bcm) since April 5, when Ukraine started the season of pumping natural gas into its reserves. As of June 29, 2019, gas reserves in the country&#39;s USFs were 21% up from 11.1 bcm reported as of June 29, 2018, while the USFs were filled by 43%, according to the state-run gas transport system operator Ukrtransgaz. In particular, 73.18 million cubic meters (mcm) of gas was injected into the storage facilities on June 29 alone. Read alsoUkraine&#39;s most important battle is for energy independence – Forbes As UNIAN reported earlier, Ukraine on April 5 started the season of pumping natural gas into its underground storage facilities. By the start of the 2018-2019 heating season, Ukraine had accumulated 17.2 bcm of gas in its underground storage facilities, which was a record high natural gas stock over the past six years. UNIAN memo. Ukrtransgaz operates 12 underground gas storages (USFs) with a total storage capacity of about 31 bcm. The USFs are an integral part of Ukraine&#39;s gas supply system and gas transit through its territory. The company is also the operator of trunk gas pipelines carrying gas from Russia to the EU. Ukrtransgaz is wholly owned by NJSC Naftogaz of Ukraine.