Panama Canal Expansion Project: How Marine Electrical Resistivity was used in Support of Canal Dredging
Gillian Noonan and Dale Rucker
Event name: 24rd EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems
Session: Geophysics in Rivers and Streams
Publication date: 10 April 2011
Info: Extended abstract, PDF ( 1.9Mb )
The Panama Canal is currently being dredged to deepen and widen the waterway for passage of larger vessels. Dredging efficiency relies heavily on knowledge of the rock type and hardness, as this will determine the dredging method and machinery selected. for example, loose sediment can be removed via suction dredging, whereas more complex drilling and blasting techniques are needed to remove harder rock types. to support this effort, a detailed marine electrical resistivity survey was completed within the Canal to produce a spatial distribution of electrical resistivity values along the canal floor to understand overall rock and sediment distribution. Resistivity data were acquired along a series of parallel, two-dimensional transects, nominally spaced 25 meters apart across the width of the navigable portion of the waterway. Alone, resistivity values could not determine rock type; it was found in this survey that differing geological units can show similar ranges of resistivity values. Although weathered and competent rock generally displays lower resistivity values and loose sediment exhibit higher resistivity, the porosity, water saturation and ionic constituents could potentially affect specific values in localized areas. This survey effort showed however, that when resistivity data are combined with known data from geological maps and Canal boreholes, rock types and geologic boundaries can be identified successfully in the resistivity data.