Diagnosing dam seepage

The Willowstick method is a proprietary geophysical process based primarily upon technology that has been named Controlled Source - Audio Frequency Domain - Magnetics (CS-AFD-M). The method was used in eliminating seepage problem in Samanalawewa Dam in Sri Lanka. Willowstick creates a primary coil by building a large primary loop that consists of the antenna wire, electrodes, and the preferential conductive pathways (groundwater) in the subsurface between the electrodes. On the 22nd October 1992 water burst out of an area downstream of the right high pool. Willowstick performed two surveys with an injection electrode placed in the reservoir. The Willowstick survey confirmed two main areas where the cut-off is compromised, closing two significant gaps in the existing supplementary grout curtain and Locating and filling major karstic features at an approximate elevation of 438mm.