The foundation of the dam comprises closely jointed hard siltstone and quartzite with overburden of decomposed rock and slope-wash up to  deep. A subsidiary embankment containing  of fill across a low saddle in a ridge forms the left abutment of the dam wall.
The dam's foundation consists of tightly packed hard siltstone and quartzite bedrock, overlaid by a layer of weathered rock and debris accumulated on the slope.  A secondary embankment made of fill material is situated across a low saddle in a ridge to form the left abutment of the dam wall.