A Case Study on Usage of Electrical Resistivity Tomography for Dam Seepage Location, Chesterfield, Missouri

Abstract

Four Electrical Resistivity Tomography (ERT) profiles and borehole data were acquired on the front face of the earth-filled dam and on the flanks, constituting Lake #1, in order to locate the seepage zone, the flow path, and to determine possible reasons of the seepage. The seepage, observed a year after the construction in the southwestern part of the lake, was severe and could cause further softening, slippage and erosion of soil, developing of pipe holes, increasing the water outflow and risk to the embankment integrity. The owner agreed to drain the lake in order to acquire geophysical and borehole data. Based on the analyses of the acquired ERT and borehole data, four solution-widened fracture zones trending from southwest to northeast were identified. It was concluded that the seepage pathway beneath the dam was through a solution-widened fracture zone, the top of which constituted the original stream channel.

Keywords

• dam seepage
• resistivity and borehole data
• fracture zone
• ERT profiles