Geophysical Surveys for Locating Buried Utilities, Lake Pontchartrain Levees, New Orleans

摘要

This report presents the results of a geophysical study performed to determine the location of buried utilities beneath or in the vicinity of the levees on the south shore of Lake Pontchartrain approximately 8 km (5 miles) north of downtown New Orleans, LA. There was concern that utilities located beneath or buried near the toe of the levees could act as a water conduit during flooding events. If a water-filled utility fails, it is possible that it may cause the levee to fail either by piping material from within the levee or cause slope stability problems. It is also possible that buried utilities can act as potential seepage paths through the levee during high water events. In this case, the buried pipe would not have to 'fail' to cause a problem. The utilities needed to be accurately located so that they could be rerouted, removed, or abandoned and grouted-in. Electromagnetic, total field magnetic, and ground penetrating radar systems were assessed to determine the best method for detecting the buried utilities in this area. The Geonics EM31 electromagnetic induction instrument was considered the most effective for detecting the utilities. EM31 anomalies, presumed to be the locations of buried utilities, were mapped and their coordinates tabulated for further interrogation.