▁found ations ▁required ▁to ▁support ▁the ▁enorm ous ▁weight ▁of ▁the ▁arch ▁and ▁load ings . ▁Con crete ▁and ▁gran ite ▁faced ▁ab ut ment ▁to wers ▁were ▁constructed , ▁with ▁the ▁ang led ▁found ations ▁built ▁into ▁their ▁sides . ▁ ▁Once ▁work ▁had ▁progress ed ▁sufficiently ▁on ▁the ▁support ▁structures , ▁a ▁giant ▁" c ree per ▁c rane " ▁was ▁ere cted ▁on ▁each ▁side ▁of ▁the ▁har bour . ▁These ▁c ran es ▁were ▁fitted ▁with ▁a ▁cr ad le , ▁and ▁then ▁used ▁to ▁ho ist ▁men ▁and ▁materials ▁into ▁position ▁to ▁allow ▁for ▁ere ction ▁of ▁the ▁steel work . ▁To ▁stabil ise ▁works ▁while ▁building ▁the ▁arch es , ▁t unn els ▁were ▁exc av ated ▁on ▁each ▁shore ▁with ▁steel ▁c ables ▁passed ▁through ▁them ▁and ▁then ▁fixed ▁to ▁the ▁upper ▁sections ▁of ▁each ▁half - arch ▁to ▁stop ▁them ▁col laps ing ▁as ▁they ▁extended ▁out wards . ▁ ▁Arch ▁construction ▁itself ▁began ▁on ▁ 2 6 ▁October ▁ 1 9 2 8 . ▁The ▁southern ▁end ▁of ▁the ▁bridge ▁was ▁worked ▁on ▁ahead ▁of ▁the ▁northern ▁end , ▁to ▁detect ▁any ▁errors ▁and ▁to ▁help ▁with ▁alignment . ▁The ▁c ran es ▁would ▁" c ree p " ▁along ▁the ▁arch es ▁as ▁they ▁were ▁constructed , ▁eventually ▁meeting ▁up ▁in ▁the ▁middle . ▁In ▁less ▁than ▁two ▁years , ▁on ▁T ues day , ▁ 1 9 ▁August ▁ 1 9 3 0 , ▁the ▁two ▁hal ves ▁of ▁the ▁arch ▁touched