Tough access and tougher-still specs led the Walsh-Alberici joint venture team to select Drilling Service Company to execute the drilling of rock sockets on the St. Charles County approach to the new I-64 Daniel Boone Bridge across the Missouri River. The site had limited access and strict environmental requirements. Drilling Service drilled 80 foot shafts using casing which Walsh-Alberici vibrated into the soil. The shafts had to be drilled under water, using the head pressure to prevent silt from seeping back into the shaft through gaps in the caisson. The bottom 20 feet of the shafts were drilled through solid rock, removing debris down to quarter-sized pieces with a water-lift vacuum and pumping it into settling ponds before returning the clean water to the Missouri.