This is one of the richest construction sources. It supports a pre-existing 520 m³ rock room, a planned 340 m³/130 m² / 1,399 ft² extension, detailed 1957-62 electrical/ventilation/water scopes, and a SEK 110,000 budget versus SEK 170,951.65 actual completion cost. Construction encountered fractured shallow rock, stoppage, changed drive direction, concrete arches/walls, bolts and substantial water/future humidity problems. It documents repeated drainage, corrosion and dehumidification work through the 1990s.

published: 520 m³ pre-conversion cavern; planned 340 m³ and 130 m² / 1,399 ft² extension; 110 m² / 1,184 ft² ceiling treatment area; shallow 5-6 m side cover in places; entry tunnel and gas/shock boundaries; fractured rock requiring arches, walls and bolts | not_published: verified final as-built extension volume; complete floor area; final cross-sections; total bolt/arch/concrete quantities; portal/escape topology

SEK 109,632 preliminary extension estimate in 1956; SEK 110,000 project budget/authorisation; SEK 75,000 initial grant; SEK 170,951.65 actual total at completion in 1962; SEK 18,331.20 installed replacement dehumidifier in 1984

24 V emergency battery/lighting; external/provisional standby-generator connection; 1,350 m³/h ventilation with 1,000 m³/h outside air; two gas/aerosol filters; 12 kW electric heater; 15 kg/day dehumidifier; water cistern and drainage; communications/alarm and electric gate; later radio-annex use

poor-rock support and changed excavation; waterproofing/drainage/dehumidification; inner partitions and structural arches; protected ventilation; electrical/comms; rework and commissioning

One converted facility; original cavern, extension and later radio-annex works form successive scopes.

Separate original-void replacement from 1957 extension project history; use 860 m³ only as an uncertain whole-facility void scenario; add a poor-rock support line based on surface area and support class; add hydro survey, drainage, waterproofing, sumps and dehumidification; use the 55% historical budget overrun as project-specific risk evidence; retain systems quantities from the detailed schedules rather than area packages

final as-built plan/section; final excavated volume; support/bolt/arch quantities; measured water inflow and drainage design; modern protection brief; current supplier rates

published planned and as-built quantities can be conflated; water and poor rock are not explicit WBS components; generic command-rock factor misses exceptional site risk; this source should calibrate risk elsewhere on the site