ers ed ▁t ube ▁tunnel ▁is ▁made ▁up ▁of ▁five ▁elements , ▁each ▁around ▁ 1 2 2 ▁metres ▁long , ▁ 2 4 . 5 ▁metres ▁wide ▁and ▁ 8 . 5 ▁metres ▁high . ▁The ▁northern ▁approach ▁was ▁formed ▁by ▁a ▁ 1 2 0 - met re - long ▁flo ated ▁open ▁' bo at ' ▁section ▁– ▁the ▁first ▁of ▁its ▁kind . ▁ ▁Ex c av ation ▁and ▁d red ging ▁D red ging ▁International ▁was ▁the ▁chosen ▁d red ging ▁contract or , ▁and ▁the ▁value ▁of ▁the ▁d red ging ▁contract ▁is ▁stated ▁by ▁them ▁at ▁€ 1 2 . 4 ▁million . ▁The ▁scope ▁of ▁works ▁consisted ▁of ▁d red ging ▁the ▁main ▁tunnel ▁tren ch ▁and ▁subsequently ▁back fill ing ▁the ▁completed ▁construction ▁with ▁sand ▁and ▁gra vel . ▁The ▁contract ▁provided ▁also ▁for ▁rest oration ▁of ▁the ▁river bed ▁profile ▁and ▁the ▁addition ▁of ▁a ▁rock ▁protection ▁layer . ▁Between ▁May ▁ 1 9 9 6 ▁and ▁March ▁ 1 9 9 9 , ▁the ▁company ▁exc av ated ▁ 7 8 5 , 0 0 0 ▁t onnes ▁of ▁s ilt ▁and ▁all u vi um ▁and ▁ 3 0 0 , 0 0 0 ▁t onnes ▁of ▁sand ▁and ▁gra vel . ▁ ▁The ▁tren ch ▁was ▁d red ged ▁primarily ▁by ▁a ▁series ▁of ▁special ised ▁vessels , ▁in ▁several ▁stages ▁and ▁with ▁different ▁equipment . ▁ ▁Much ▁of ▁the ▁main ▁tren ch ▁for ▁the ▁Lee ▁T unnel ▁was ▁exc