Frostpunk 2

At the start of chapter 4, you have to choose whether you want to salvage Winterhome or colonize it? Choose salvage. Immediately start frostbreaking your way towards the different core deposits. (iirc, there are 10.) After first round of core extraction, you'll get the option to build automation workforce, so that citizens don't work in toxic fumes. Build a few industrial districts, and then place the Automated Workforce building in them. Your workforce number will jump. Keep frostbreaking towards all core deposits and then building extraction districts on them.

Once you recover 40 cores, you'll get an option to evacuate and go back to New London. Decline that and choose to extract all cores. Check the "next gas outburst" time remaining at the top left of the screen. You have to extract all remaining cores (I think ~20 cores remain at that point.) before that. Click all the core deposits to see how much time it'll take to extract all cores from them. If the highest number is lower than timer at top left, then you are good. If not, try using the emergency shift thing and that should help hasten it up.

After you extract all cores, switch to New London, build the generator regulator thingy and transfer the maximum allowed number of people from Winterhome to NL. Then the achievement will pop.