|The petrol tanks, from the side.
Tech notes: upon reviewing my recordings, there was an exceptional amount of low frequency rumble from this tank. It was easily scrubbed by applying a High-Pass Filter at 129Hz. I kept some alternate takes with the HPF set at 96Hz, which sound much bigger but not as clean. A lot of the MDF plant's shenanigans is in that very low band.
|The larger tank, you can just see the perforation in the shadow to the left.
|The hatch. Apologies for the cropping - I was using my telephoto lens.
Tech notes: these recordings required some subtle noise-reduction as well as the HPF treatment. I found that the pebble drops leaned towards the higher end of the audio spectrum, so weren't negatively affected as much by the HPF as the other sounds.
|The pipes. Most are metal, but you can see a couple of plastic/polymer ones in the upper left.
|The pipes are approx 18" in diameter, with walls an inch thick.
|The view down one of the plastic pipes. Overexposed to show the interior walls.