"I can’t remember anymore what it sounded like when all the machines were up and running. Machines were humming and whirring, the ventilation ducts were in operation, the electrics produced light. People – humiliated by the difficulty of the work and the darkness which enveloped them in hopelessness – groaned, moaned and wept as uniformed Germans marched up and down the stairs to maintain their omnipotent control: to submit these innocent, unsuspecting people to this martyrdom."
Forced labour dictated the daily routine of prisoners in the concentration camps at Porta Westfalica. Work was generally carried out in twelve-hour shifts, seven days a week. Only on Sundays were there half shifts as this was when the weekly rotation from day to night shifts would begin.
Until the summer of 1944, the prisoners from Barkhausen were mainly assigned to unskilled labour. Civilian miners, which also included those sent by the Gewerkschaft Porta in Dützen, blew up new tunnels in the Jakobsberg. The rubble then had to be removed by hand using only a shovel, pickaxe and wheelbarrow. The work was physically demanding with abuse taking place; the food supply was far from adequate. The first documented death occurred after only two and a half weeks. Not long after, the first group of exhausted prisoners was transported back to Neuengamme and replaced by new prisoners. The name Hölle I (Hell I) became popular among the prisoners for the lower tunnel system in the Jakobsberg, which was known as Höhle I (Cave I).
In total, it only took around three months to develop the 1,500 square metres of tunnel floor space to the initially given target size of 5,000 square metres. According to a report by the Allies after the war, approximately 60,000 cubic metres of rock had been mined for the tunnel system during the twelve months of construction work. With the mining work at the Jakobsberg temporarily completed, a shift of construction activities to other underground sites at Porta Westfalica, and the reassignment of Höhle I (Cave I) to a Deurag-Nerag refinery, the forms of forced labour for the prisoners also changed.