Disclaimer: The Purdue Outing Club does not condone illegal or dangerous activity. Entering confined spaces without the proper training or equipment is extremely dangerous and you should not do it.
Two major storm sewer drainages exist at Purdue Ross-Ade Stadium to the holding pond near Wade Utility Plant, and main campus drainage. Warning: main campus drainage has organic flow from animal science and biology labs (ever see Indiana Jones and the Temple of Doom?) you better like cockroaches.
The Ross-Ade Stadium is just a diverted stream and is clean. At about the CoRec the culvert descends at a 45 degree angle which makes a great waterslide.
Numerous expeditions were led by caving chairman John Roeder, POC President John Harrell. Also Rob Acker was known to frequent the underworld.