NL ▁status . ▁The ▁quar ry ▁company ▁chose ▁to ▁honor ▁the ▁N NL ▁status , ▁separ ating ▁the ▁ca vern ▁property ▁from ▁the ▁remainder ▁of ▁the ▁quar ry , ▁which ▁is ▁still ▁in ▁production ▁today . ▁ ▁Development ▁SN RC ▁purchased ▁Black ▁Ch asm ▁Ca vern ▁in ▁ 1 9 9 6 ▁and ▁began ▁offering ▁ 5   hour ▁expedition ▁tri ps , ▁including ▁rapp elling , ▁ra ft ing , ▁clim bing , ▁and ▁craw ling ▁through ▁the ▁wild ▁areas ▁of ▁the ▁cave . ▁These ▁tri ps ▁ran ▁for ▁four ▁sum mers ▁before ▁damage ▁to ▁the ▁del icate ▁areas ▁of ▁the ▁cave ▁was ▁de emed ▁too ▁ste ep ▁a ▁price ▁to ▁continue ▁offering ▁t ours ▁through ▁the ▁wild ▁cave . ▁In ▁ 1 9 9 9 , ▁development ▁began ▁on ▁the ▁property , ▁which ▁included ▁creating ▁a ▁road , ▁sept ic ▁and ▁utility ▁installation , ▁and ▁building ▁storage ▁facilities . ▁St air ▁building ▁into ▁the ▁ca vern ▁began ▁in ▁July ▁ 2 0 0 0 , ▁with ▁the ▁first ▁walking ▁t ours ▁being ▁offered ▁on ▁the ▁last ▁week end ▁in ▁September ▁ 2 0 0 0 . ▁The ▁trail - building ▁sp anned ▁just ▁over ▁ 1 0   month s , ▁as ▁the ▁crew ▁frequently ▁har ness ed ▁up ▁and ▁used ▁ro pes ▁for ▁the ▁construction ▁process . ▁Though ▁intro duct ory ▁t ours ▁were ▁being ▁conducted ▁during ▁the ▁st air ▁construction ▁period , ▁the ▁grand ▁opening ▁of ▁Black ▁Ch asm ▁took ▁place ▁in ▁April ▁ 2 0 0 1 .