After the maintenance, I dug.
A steel pipe end peeked out. Regular readers will not be surprised that this led to half the Nordstream pipeline coming out.
Then I dug out the side of the big barn, because it's bottom log is rotting from being below soil level due to 90 years of soil accumulation. Good practice for digging near buildings. Only hit the roof once
Lots more junk came up, steel, chunks of cancer roofing, wire, wood, roots, rubber, plastic pipe, disintegrating plastic sheet, rocks and lots of bricks.
Then I made a ditch for the water from the roof to run off (there's no gutter) and leveled the area. Needs some more infill at the end, but already much better.