fogg has used Project-GC to see if they qualified for this challenge and they did.
I found all 1 needed caches with at least -1 Elevation
GC338E -4927 2003-11-04 A Pair of Quintuplets (Multi-Location Virtual)
I found in fact also physical caches with negative elevation, e.g. GC2WM6R
Fogg & Consortin