▁ca vers ' ▁collect ive ▁responsible ▁for ▁expl oring ▁the ▁Rey f ad ▁system . ▁The ▁entrance ▁was ▁made ▁in ▁a ▁sh ake hole ▁adjacent ▁to ▁the ▁sink ▁point ▁of ▁the ▁H une ▁( pr on ounced ▁" h oney ") ▁stream , ▁and ▁close ▁the ▁border ▁in ▁County ▁Cav an . ▁This ▁entrance ▁became ▁known ▁as ▁" Pol lah une ". ▁The ▁initial ▁route ▁was ▁d ug ▁through ▁a ▁highly ▁un stable ▁area ▁of ▁gla cial ▁fill , ▁making ▁it ▁extremely ▁tre acher ous . ▁Once ▁in ▁the ▁cave ▁the ▁ca vers ▁encountered ▁a ▁" main " ▁stream way ▁into ▁which ▁the ▁H une ▁flow ed , ▁with ▁the ▁up stream ▁section ▁leading ▁to ▁" J CP ▁Pass age " ▁and ▁the ▁down stream ▁section ▁passing ▁another ▁significant ▁in let , ▁" M ist ake ▁Pass age ". ▁By ▁the ▁end ▁of ▁August , ▁the ▁team ▁had ▁progress ed ▁past ▁several ▁b ould er ▁ch okes ▁and ▁expl ored ▁cave ▁pass ages ▁some ▁ ▁in ▁length . ▁ ▁Down stream , ▁the ▁team ▁reached ▁a ▁termin us ▁at ▁a ▁prominent ▁b ould er ▁cho ke , ▁through ▁which ▁they ▁attempted ▁to ▁dig . ▁In ▁October ▁ 1 9 8 0 ▁a ▁section ▁of ▁the ▁cho ke ▁col lapsed ▁on ▁Rev . ▁George ▁Pitt ▁while ▁he ▁attempted ▁to ▁force ▁a ▁passage ▁at ▁river ▁level . ▁He ▁became ▁tra pped ▁for ▁ 1 0 ▁hours , ▁but ▁was ▁fre ed ▁after ▁a ▁major ▁rescue ▁effort . ▁By ▁ 1 9 9 0 ▁the ▁expl