History and specifics
The planet was a predominantly oceanic world, with only mountain peaks standing above sea-level. However, it was also rich in valuable trace elements and minerals, such as dilithium, bilitrium, kelbonite and others.
The native Dai-ai made an agreement with the Federation to allow the Starfleet Corps of Engineers (SCE) to conduct mining operations on Naia VII, which were underway by 2368 under the command of Captain Ochoa. These operations were partially classified, but Starfleet gained raw materials vital to its defense while, in exchange, the Dai-ai were amply compensated with food and supplies.
However, the Dai-ai had firm environmental regulations that disallowed particle beam– and transporter-based mining technologies—essentially, not wishing anyone to fire on the planet. This necessitated traditional and dangerous excavation methods, tunnelling directly into the sunken mountains. The mining operations were an engineering achievement, but also quite difficult and dangerous, as the SCE miners had specific quotas to meet despite the dangers, which led to reduced safety standards. To guard against leaks and high pressure, they used force fields, sealants, interlocking pressure compartments, and anti-gravity technology.
Due to the dangers, Ochoa requested that another Starfleet vessel visit the world to provide technical assistance. The USS Enterprise-D was sent, and shortly before stardate 45635, Ochoa and Lieutenant Amato met with Commander William Riker, Lieutenant Commander Data and Lieutenant Worf of the Enterprise. Ochoa introduced them to Seelos, a Dai-ai native to Naia VII, then showed the visitors around the mine works. When a burst pressure compartment flooded a mine, Worf rescued Ochoa and Amato, but eight people were killed and twenty-two more were injured.
Following the disaster, the Enterprise was able to request extra support for the Naia VII mining operation. The USS Lexington was sent with additional personnel and equipment. (TNG - Assimilation² comic: "Issue 2")