Drilling is done in water that is from ten to ninety feet deep.
Probes can test for strength of soil and composition.
To plan for the construction of the new East Spans of the San Francisco-Oakland Bay Bridge, investigations must be made of the soil conditions on and beneath the floor of San Francisco Bay. Caltrans has contracted with Fugro-Earth Mechanics (a joint venture) to perform these investigations.
Since February, 1998, around-the-clock drilling and testing has taken place north of the existing east spans of the Bay Bridge. Drilling crews and geotechnical engineers have been gathering data that will provide necessary information for bridge designers and builders.
In this work, a pipe is first lowered from barge-mounted drill rig to the top of the bay mud and seated before sampling and testing begins. The probes and samplers are drilled or forced through the bay floor to depths of just a few inches all the way to over three hundred feet. The outer pipe prevents disturbed bay mud from mixing with the bay waters. Once a hole is completed, this same pipe is used to fill the hole with grout to prevent any mixing with bay waters. During the drilling, all drilling mud and lubricants are recirculated and recovered for safe disposal.
A laboratory on the barge provides immediate information about the samples which helps to guide the drillers in their work.
The information gathered not only becomes the basis for the design of the bridge piers but also gives the pile drivers an extremely accurate representation of what kind of soils they will be going through to predict their schedule and costs when bidding for this work.