All Systems Go

At Brennan, we utilize hydrographic survey systems to measure progress on all of our dredging projects. These systems typically include a positioning system, such as RTK-GPS, and a multi-beam echo-sounder. The Real Time Kinematic, Global Positioning System, or RTK-GPS, is a precise satellite navigation tool, whereas an echo-sounder is a sonar device for measuring depth. Combining the two allows us to achieve very accurate measurements on the location of the river bottom. We take the data points created during these measurements and create a 3-dimensional model using Hypack® software. By running a survey before we dredge, and then one afterward, we can create two models and compare them to one another. The difference between the two models is the total volume of in-situ yardage that we have removed. Typically, we are paid by the in-situ volume of sediment (in cubic yards) that we remove so it is very important that these measurements are extremely accurate. Therefore, establishing quality control checks on the equipment before we survey is an extremely important step in achieving accurate measurements.

According to the United States Department of Transportation, underwater scour is the leading cause of bridge failure, ahead of collisions and overloading. Scour is the erosion or removal of a streambed or bank material from bridge foundations due to flowing water. As many bridges sit over water, the potential dangers of scour cannot be ignored. There are many solutions to scour problems. However, there are two options that we find the most effective.

Dredging around utilities is challenging, and mistakes can be expensive and dangerous. When utilities, such as power lines, natural gas lines or fiber optics, are above ground they can be easily marked, and a plan can be developed to avoid them. However, when these same utilities are underwater, locating them and working around them adds an additional layer of risk for the contractor.

Turbidity is a hot-button issue in the environmental dredging industry because if it is not controlled, contamination can spread to clean areas. Since every dredge project will experience the presence of suspended sediments in the water column, proper measures are taken to control this problem.