I can only find two of the textures and it doesnt even cover that much of the base:
See the texture in the rim of the opening in front of the warthog? thats and the lights are the only ones I can find
Not 100% sure, but I think levels\b30\bitmaps\detail ground is the texture for the top of the base. levels\test\bloodgulch\bitmaps\cap_ramp01 and levels\test\bloodgulch\bitmaps\cap_ramp02 are the floors to the bases. If you look under bitmaps, mostly b30 and test\bloodgulch are used.
damnit... that would make sense. I was thinking since it was in b30 it wouldnt be used.. but why would they have the same texture named twice right? lol Thanks man!