This idea is still being worked out, so I apologize if some of my points are too obtuse.
In The Book of the Dead, the section entitled “Power” literally details a tour of a power-plant, but figuratively explores a descent into a both literary and personal Darkness. At the beginning of the poem, words like “brilliant”, “light-pointed”, and “skin-white” craft an image of Heaven, an idealistic zone of pure intention and good thought.
Below this lies “the road to take when you think of your country”, a power-plant of “grey-toned” stone but with light shining “from three-story windows”. This is the Earth, a gritty place dominated by man-made objects, no longer containing the immediate “brilliance” of Heaven, but with light still observable from a distance. Here resides the human experience and sense of identity within themselves and their environs, and it is no coincidence that a human provides a tour of this facility of self-reflection.
In case the stratification of the planes and the descent through them isn’t apparent, Rukeyser calls the next level the “world of inner shade”, the “second circle”, a reference to the circles of Hell in Dante’s Inferno. The second circle, Gluttony, is the dark center of the human, the cold heart of the power-plant. The planned tunnel is by humans for humans, but once veneers of quality of life improvements, providing jobs, and industrial progress are stripped away from the concept, the plant is created and funded for one common purpose:to provide wealth to the elite who crave it, at the cost of others’ capital, labor, and lives.
The ultimate conclusion to this ravenous appetite for wealth is provided from the bottom level, the “after-night”: Death itself. Here is the unsalvagable, “all the light burns out”. You “cannot ascend”. Here the lies eternally echo on the pitch-black tunnel walls, a monologue of deceit and self-justification who’s only audience are the damned and the dead. This is the resultant of the subjugation of nature and the human, of the allowance of idle selfishness to ignore the plight of the silenced worker. “This”, as Rukeyser ominously prophisizes, “is the end”.