Using Geophysics to Streamline a Seepage Investigation at Moore Dam

Seepage downstream of the Moore Dam embankment has been an on-going issue for many years. The seepage was assumed to mostly originate in the abutment to the north of the dam embankment and was remediated with a filter drain in 1996. Field investigations were undertaken to investigate the sources of the seepage following failure of the filter drain in 2009. Spontaneous potential (SP) and resistivity imaging surveys were conducted in an area downstream of the embankment and were used to identify the most suitable locations for borings and piezometers. The geophysical results were used to locate the borings, thereby cutting down the number of planned explorations by about half. The geophysical investigation was a cost effective tool that allowed the team to select appropriate locations for borings and piezometers and confirmed the existence of subsurface features included in the dam design and seepage patterns in the dam and abutment.