▁H idden ▁mine ▁sh aft s , ▁often ▁hidden ▁beneath ▁bush es ▁and ▁grass es ▁and ▁other ▁veget ation ▁that ▁has ▁grown ▁up ▁around ▁the ▁mine ▁entrance ▁ ▁Un stable ▁roof s ▁and ▁passage ways , ▁pr one ▁to ▁cave - ins ▁ ▁Ab andon ed ▁M ines ▁in ▁the ▁United ▁States ▁ ▁De fin itions ▁▁ ▁Department ▁of ▁the ▁Inter ior ▁- ▁Bureau ▁of ▁Land ▁Management ▁- ▁Ab andon ed ▁mines ▁are ▁those ▁mines ▁that ▁were ▁abandoned ▁prior ▁to ▁January ▁ 1 , ▁ 1 9 8 1 , ▁the ▁effective ▁date ▁of ▁the ▁Bureau ▁of ▁Land ▁Management ' s ▁Sur face ▁Management ▁reg ulations ▁issued ▁under ▁authority ▁of ▁the ▁Federal ▁Land ▁Policy ▁and ▁Management ▁Act ▁of ▁ 1 9 7 6 , ▁as ▁am ended ▁( 4 3 ▁U . S . C . ▁ 1 7 0 1 ▁et ▁seq .) ▁ ▁Environment al ▁Prote ction ▁Agency ▁- ▁Ab andon ed ▁mine ▁lands ▁( AML s ) ▁are ▁those ▁lands , ▁waters ▁and ▁surrounding ▁waters h eds ▁where ▁extra ction , ▁benef ici ation ▁or ▁processing ▁of ▁or es ▁and ▁min er als ▁has ▁occurred . ▁ ▁In ▁the ▁United ▁States ▁there ▁are ▁thousands ▁of ▁abandoned ▁mines . ▁The ▁precise ▁number ▁of ▁abandoned ▁mines ▁in ▁the ▁United ▁States ▁remains ▁unknown , ▁r anging ▁" from ▁the ▁National ▁Park ▁Service ' s ▁t ally ▁of ▁ 2 , 5 0 0 ▁on ▁its ▁lands , ▁to ▁the ▁Min eral ▁Policy ▁Center ' s ▁assess ment ▁of ▁ 5 6 0 ,