- Cleveland Bridge California Inc., FCI Contractors JV
- California, USA
- PBA 928
In 2000 the contract for the new Carquinez Bridge was awarded to the joint venture of FCI contractors and Cleveland Bridge.
Each foot of the bridge tower is supported by 6 vertical 3 m diameter steel shells infilled with reinforced concrete. Followed by 2,7 m diameter drilled shafts in rock. Total average depth 89 m of which 43 m drilled in rock by under-reaming.
A closed circulation system is used for the cuttings consisting of shakers to remove solids and containers in which the mud can settle.
The job was executed with the Wirth PBA 928 with hydraulically operating power-swivel of 280 kNm and using the reversed airlift drilling principal for soil removal. Drill bits of 2850 mm, 2700-3300 mm and 2000 mm diameter are used. The bottom hole assembly was equipped with steel brushes to clean the shell wall.