17 5 U ndergr ound W or kings Entr y Initial in v estigation should be staged e xamine stat e of v entilation condition of tunnel back and sides and presence of w at er A dv ance only when saf e t o do so and check back t o por tal at freq uent int er v als Do no t s am ple or break r ocks on initial e xplorat or y inspection thr ough the w or kings R e treat immediat ely if old ti mber s ha v e collapsed or r ock has f allen fr om backs or raises Ev en so lidlooking timber s ma y be com ple t ely r o tt en and ha v e no strength check with scaling bar R e treat immediat ely and abandon all plans if there is an y indication of a danger ous atmosphere eg o xy gen defcient t o xic fammable or e xplosiv e f or fur ther immediat e in v estigation U ndergr oun d v entilation can change fr om da y t o da y and o xy gen cont ent can dr op t o zer o in a horizontal distance of 1 0 me tres Whe n undergr ound do no t separat e fr om y our cre w Sam pling of mineralized structures and w allr ocks ma y be under tak en only af t er de t ermining that the w or kings are saf e use common sense Continued In v estigation An y e xtraction of r ock req uires a cer tifed shif tboss t o be on sit e If undergr ound sam pling is necessar y the ser vices of a suitably q ualifed shif tboss with a v alid BC Mines Shif tboss cer tifcat e must be obtained