Determining Sludge Thickness Using Sonar Mapping of Ponds at a Midwest Refining Company


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Determining Sludge Thickness Using Sonar Mapping of Ponds at a Midwest Refining Company

Understanding and tracking available volume of industrial or commercial lagoons and ponds are critical to the effective management of wastewater and stormwater systems. Over the years, solids accumulate in the bottom of lagoons and ponds, decreasing the available storage capacity and, in some cases, allowing the unintended discharge of solids. A Midwest international refining company asked Cox-Colvin & Associates (Cox-Colvin) to conduct a sonar mapping survey on several of their industrial ponds to determine the volume of sludge present in the lagoons and to collect samples of the sludge for dredging and disposal purposes. For one of the ponds with no design or as built drawings, additional information was necessary for a permit modification for the pond.

Cox-Colvin conducted surveys of the ponds using Sonar/GPS to determine the thickness of sludge and to calculate the capacity of each pond.  This information was critical in determining costs for the removal/dredging of the sludge.  Post-dredging Sonar/GPS work was used to determine effectiveness of removal operations and became the baseline for calculating future rates of sludge accumulation.  Samples of the sludge were analyzed, and that information was used to characterize the sludge for disposal.  In addition, the results of the survey indicated that the wastewater system was not working as intended and that sand was being discharges from the Wastewater Treatment Plants (WWTP) sand filters into to pond.  Annual surveys are now completed on the ponds.