Two major Storm Sewer drainages exist at Purdue Ross-Aid Stadium to holding pond near Power 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-Aid Stadium is just a diverted stream and is clean. At about the Co-Rec the culvert descends at a 45 degree angle which makes a great water slide.
Numerous expeditions were lead by Caving Chairman John Roeder, POC President John Harrell. Also Rob Acker was known to frequent the underworld.