Contractor EPOS driving twin 900 m x 75 m² tubes in weathered granite using umbrella drilling where necessary. Two Atlas Copco L2C drillrigs carry out all drilling for blasting, rockbolts, and umbrellas, the latter using 64 mm bits on extension steel. Steel arches, Swellex 4 m rockbolts and shotcrete form main support. More information from pdc@epos.pt . October 1999.
