How to improve my low note range?

ok soo basically my story is this: i've been in choir since my freshman year .. and i started off as a tenor in 9th grade.. and a tenor in 10th grade and for the first half of 11th grade i kept doing tenor but then i started doing base 2 because my voice has naturally gotten ALOT deeper.. lol, anyway.. the weird thing about me is that i can sing tenor 1 range perfectly well.. but i can also sing a base 2 range perfectly well.. i think my lowest note is a .. low D? idk maybe a low D or F.. thats about my lowest note and most of the songs we sing dont demand too much as far as range goes.. i just want to know if theres any way to develop my voice a bit more through some sort of excersise so that i could sing the lowest notes of a base (like a low C, B, A, or G.. it's lower than my low D or low F... those are some LOOWWWWWW notes! haha) any help or advice would be greatly appreciated!