what example of wast does Marlow see around the company buildings?

“At last we opened a reach. A rocky cliff appeared, mounds of turned-up earth by the shore, houses on a hill, others with iron roofs, amongst a waste of excavations, or hanging to the declivity. A continuous noise of the rapids above hovered over this scene of inhabited devastation. A lot of people, mostly black and naked, moved about like ants. A jetty projected into the river. A blinding sunlight drowned all this at times in a sudden recrudescence of glare. ‘There’s your Company’s station,’ said the Swede, pointing to three wooden barrack-like structures on the rocky slope. ‘I will send your things up. Four boxes did you say? So. Farewell.’

“I came upon a boiler wallowing in the grass, then found a path leading up the hill. It turned aside for the boulders, and also for an undersized railway-truck lying there on its back with its wheels in the air. One was off. The thing looked as dead as the carcass of some animal. I came upon more pieces of decaying machinery, a stack of rusty rails. To the left a clump of trees made a shady spot, where dark things seemed to stir feebly. I blinked, the path was steep. A horn tooted to the right, and I saw the black people run. A heavy and dull detonation shook the ground, a puff of smoke came out of the cliff, and that was all. No change appeared on the face of the rock. They were building a railway. The cliff was not in the way or anything; but this objectless blasting was all the work going on."

Both quotes are from Part I, page 9; They are working around the building, construction in everywhere. The area looks like a wastelend and is a complete mess, but that's all the work to be seen. The waste itself is everywhere, and it isn't like it's new waste; objects are rusty. They've been misused and neglected; there's no rhyme or reason to what he sees.