RITSUKO:“The very first ones. They are the failures.
They were scrapped ten years ago.”
SHINJI (OFF):“A graveyard for Evas...”
RITSUKO (OFF):“It's just a garbage dump.
This is also where your mother disappeared.
You may not remember it, but I believe you were also watching
the very moment your mother vanished.”
UrsusArctos: Ritsuko makes the Eva Graveyard here to be the site of Yui's Contact Experiment. We never get a look at Eva-01 or the rest of the facility beyond the control booth in Episode 21, but the implication is that Eva-01 was still growing from Lilith. This isn't just a dumping ground for failed Evas, it's also the birthplace of Eva-01. All the pits and channels probably housed Eva-01 and Lilith at one point of time, or were apparatus for growing Evas.