New high resolution underwater imaging sonars (operating at between 700kHz and 3.000 kHz) allow us to see underwater (even in the murkiest waterway such as the Houston Ship Channel) with clarity never achieved before. CRA has performed such a survey to locate objects (Exon Baytown refinery) and to look at the underwater condition of a sheet pile bulkhead at the ITC docks in Houston. The latter image (seen above) took just one hour in the field. The object is to be able to scan a bulkhead quickly and relatively inexpensively to see if any areas need intervention by a diver to either investigate specific areas in more detail or to actually fix the problem.
Small remotely operated vehicles (ROVs) are now powerful enough and inexpensive enough to bring a great deal of capability to the inspection of underwater structures, be they sheet pile bulkheads, concrete dams, or bridge piers as they can carry not only video cameras, but the new high resolution sonars that can produce an image even in water too murky for light-based systems.
CRA has recently successfully completed several projects with the “Echoscope” 3D multi-beam sonar, which is a high resolution system usually mounted on a special over-the-side rig on our new survey vessel. The equipment gives very crisp detailed images of the vertical faces of a dock structure or bulkhead.